- Email: [email protected]
Effects of ultrasonic radiation in experimental focal epilepsy in the cat
EXPERIMENTAL
Effects
NEUROLOGY
of
10,
MANLAPAZ,
(1964)
Ultrasonic Focal
J. S.
345-356
K.E.
Radiation
Epilepsy
in
in the
Experimental Cat
H. T. BALLANTINE,
ASTR~M,
JR., AND P. P. LELE~
Medical Acoustics Research Group, Massachusetts General Hospital, Boston, Massachusetts Received
April
15, 1964
Introduction Experimental focal epilepsy was induced in thirty-seven cats by subcortical injection of 0.1 ml of alumina cream. Fifteen of these were treated by surgical removal of the epileptogenic focus, twelve by irradiation with focused ultrasound and nine with medication. One died before any therapy could be instituted. Ultrasonic irradiation effectively relieved the animals of the seizures and abnormal EEG patterns by eradication of the epileptogenic focus with less untoward effects and postoperative complications than did surgery. Medical therapy was ineffective. Post-mortem examination of the brains showed grossly that ultrasonic irradiation eradicated the epileptogenic focus without destroying extensively the overlying and adjacent brain tissue and without forming corticodural adhesions. Microscopically, irradiated foci could be distinguished from the surgically treated ones by inter alia absence of trabeculated loose vascular scar tissue and paucity of fibroblasts and collagen fibers. Introduction
Post-traumatic focal epilepsy is surgically treated by ablation of the focus and cranioplasty if indicated, This is not entirely satisfactory becauseof the inadequacy of control over the volume of the tissue removed (and traumatized) and the possibility of recurrence due to damageto the leptomeningesand local vasculature and the formation of corticodural adhesions (14). Focused ultrasonic radiation (11) which has been shown to be the method of choice for trackless destruction of discrete, predetermined volumes of tissue at any preselected region within the central nervous system, without any undesired damage to the other adjacent 1 This investigation was carried out under a Research Contract with of the Surgeon General, U.S. Army Medical Research and Development and supported in part by the U.S. Public Health Service. 345
the Office Command
346
MANLAPAZ
ET
AL.
tissue (2), appears to be ideally suited for treatment of focal epilepsy. The ultrasonic lesion has simple and unvarying neurophathological features (1) irrespective of the species and the age of the animal (20) and the resultant scar is of a very low epileptogenic potential (3). This study was undertaken to determine if ablation of epileptogenic foci by ultrasonic radiation transdurally is, in fact, superior to current surgical methods. For this study, experimental focal epilepsy was induced in cats by subcortical injection of alumina cream (10). Materials
and
Methods
Forty-five healthy adult cats were used. In each, under light pentobarbital anesthesia (25 mg/kg) , control electroencephalograms (EEG) were recorded from needle electrodes placed in standard positions over frontal, temporal, parietal and occipital regions bilaterally. The animal was then placed in a stereotaxic apparatus and a trephine hole 1 cm in diameter was made in the left frontoparietal region of the skull, after incision and retraction of the scalp and underlying tissues. Using a tuberculin syringe with a 22-gauge needle, 0.1 ml of alumina cream was injected slowly 2 mm below the cortical surface of either the middle suprasylvian gyrus (thirty-six cats) or the anterior sigmoid gyrus (nine cats), the former being preferred since it obviates opening of the frontal sinus which frequently leads to meningitis or respiratory infection or both. The wound was closed and the animal was then observed for abnormal motor activity for a period of 12 weeks. The EEG was recorded at weekly intervals throughout the experiment. After the first seizure, the animal was treated either surgically (fifteen cats) or by ultrasonic irradiation (twelve cats) with a dose calculated to create a lesion 15 mm long and 5 mm in diameter in normal brain (2). As a control, nine cats each were given 15 mg of sodium phenobarbital and 100 mg dilantin every day, orally when conscious or parenterally when unconscious. For surgical ablation, the previous trephine hole was enlarged under anesthesia, the dura mater was slit across the scar of the needle puncture, and the alumina cream removed by suction. The wound was closed after hemostasis. For ultrasonic irradiation, an adequate craniectomy (11) was performed and the precalculated dosage of ultrasound was delivered 2 mm below the site of injection of alumina cream. The EEG was recorded immediately after treatment and at weekly intervals thereafter for 12 weeks during which the animal was observed for seizures. It was then killed and the brain removed for subsequent
FOCAL
EPILEPSY
preparation of sections stained with H & E, cresyl violet and stain. Since subcortical application of alumina cream commonly seizures within 4 to 6 weeks (lo), animals which had not had zures or did not display an abnormal EEG till 12 weeks after of alumina cream were excluded from this study.
347
a myelin induces any seiinjection
Results
No neurological abnormality was apparent immediately following the injection of alumina cream. Of the forty-five operated animals, five died of pulmonary infection within a week of the operation. Four of the forty surviving cats (10%) developed seizures during the fourth week following the injection of alumina cream and thirty-three additional ones ( 83y0) in the succeeding 2 weeks. Three (770) showed no abnormalities for 12 weeks and were excluded from the study. The incidence or the time of onset of seizures after injection of alumina cream was not related to the site of injection, The seizures were preceded by circling, usually in a direction opposite the site of lesion, jerking of the head from side to side, followed by an audible cry; then the animal went into clonic convulsions involving the whole body. Dilatation of the pupils, fluttering of the eyelids, salivation and, on occasion, urination and defecation occurred. The convulsive phenomena lasted 15 set to 2 min and recurred every 5 to 10 min. The animal remained unconscious and flaccid after the seizure and did not regain full consciousness during the interval between the seizures. In one cat the interval between the seizures diminished, it developed epilepsia partialis continua opposite the side of the lesion and succumbed in status epilepticus before any treatment could be initiated. The EEG in the preinjection control period showed low-voltage, well organized, alpha mixed with theta rhythms (Fig. 1A & 3A). This remained unchanged after injection of alumina cream (Fig. 1B & 3B) until just prior to the onset of seizures (Fig. 1C & 3C). At this time the pattern was moderately disorganized and showed predominant beta rhythm with random paroxysmal bursts of medium- to high-voltage sharp wave and spike activity localized over the site of injection. The rest of the record was a mixture of alpha and beta rhythms. During the convulsive phase, the record became flat or nearly isoelectric in all leads for 2 to 5 min and then it reverted back to its original pattern. Pathological examination of the brains of cats which died in status
348
MANLAPAZ
ET
AL.
epilepticus showed grossly a fibrotic thickening of the external surface of the dura mater underlying the craniotomy. The inner surfaces of the dura and the leptomeningeswere smooth and without adhesions.A small rounded elevation was seen on the surface of the brain at the site of penetration of the injection needle. The surrounding areas of the same gyrus were smooth. Coronal sectioning disclosed a rounded mass of alumina cream, which had distended the gyrus and destroyed and replaced its white matter, similar to that in Fig. 4. In some instances the alumina cream was completely situated beneath the cortex which was stretched out and thinned. In other cases it had encroached upon and more or less destroyed the overlying gray matter, specially at the crown of the gyrus, as in Fig. 5. Microscopically, the lesion itself could be divided into two zones. The peripheral region consisted of a cellular granulation tissue with blood vessels, fibroblasts, rather large and free globules of alumina cream, macrophagesand a small number of inflammatory cells, e.g. lymphocytes, monocytes and plasma cells, as in Fig. 6. The center of the lesion was avascular; it seemedto contain a fluid in which a few macrophagesand alumina cream globules were suspended.The lesion was enveloped by a thin capsuleof blood vessels,frbroblasts, astrocytes and inflammatory cells. The cortex surrounding the lesion was thinned and showed extensive disorganization of cell pattern. All nerve cells had disappeared in the crown of the gyrus. There was also an extensive destruction within the other areas of the cortex adjacent to the lesion, i.e., those parts which faced the nearby sulci, where a majority of nerve cells had disappeared. Some of the remaining nerve cells appeared degenerate, dark and shrunken or very pale and frequently vacuolated. The best preserved nerve cells were found in the superficial cortical layers and the destruction appeared to increase towards the lesion. The cortex in adjacent gyri was usually well preserved, although a number of degenerated nerve cells were seen occasionally, specially in areas neighboring upon the lesion and its overlying cortex. Thus, the cortical region at the bottom of the sulci on both sides of the alumina cream mass always contained many degenerated cells and the destruction increased towards the lesion. There was an intense astrogliosis and proliferation of microglia cells within the areas of nerve cell destruction, and depopulation of nerve fibers and astrogliosis in the white matter surrounding the lesion. SurgicaZ Ablation. Six of the fifteen animals so treated died from postoperative complications (Table 1). The death was attributed to
FOCAL
349
EPILEPSY
surgical shock and cerebral edema in two and pulmonary infection in four. Eight of the nine surviving cats were relieved of seizures and remained so for 12 weeks, when they were killed. The remaining animal also was relieved of seizures after the ablation, but these recurred with reduced frequency and severity 3 weeks later. It was noted, however, that after each seizure this cat immediately regained full consciousness, shook its body and licked its fur as if nothing abnormal had happened; whereas, prior to the ablation it had failed to regain full consciousness after seizure. This cat continued to have seizures two to three times a week for 8 weeks, at which time the wound was opened for exploration with considerable difficulty due to extensive adhesions. The site of ablation was found to have been 5 mm anterior to the alumina cream lesion. TABLE NUMERICAL
RESULTS
Total number treated Died of postoperative complications Rendered seizure-free a Died
in status
OF TREAI-MENT
1 OF EXPERIMENTAL
FOCAL
Surgical
Ultrasonic
15
12
6 8
1 9
EPILEPSY Medical 9 9a 0
epilepticus.
After surgical ablation of the epileptogenic focus the EEG generally showed a predominance of low-voltage alpha rhythm with complete extinction of sharp waves and spikes (Fig. ID), except in the above animal in which paroxysmal bursts of high-voltage sharp waves and spikes were found to persist, though with reduced frequency. Pathological examination of these brains showed grossly a fibrotic thickening of the meninges with adhesions at the site of the surgical ablation. The gyrus was shrunken, the surface scarred and shriveled and its central region contained loose trabeculated and sometimes cystic scar tissue (Fig. 2). Alumina cream was seen grossly in the one animal noted above. Microscopically, the cortex overlying the lesion showed a defect which in most cases was confined to the crown of the gyrus. The adjacent areas of the cortex were fairly well preserved although many neurons showed signs of degeneration, specially in the deeper layers of the cortex, except in some cases in which it was extensively destroyed. The main part of the lesion consisted of a rather loose scar tissue which was made of astrocytes, blood vessels, fibroblasts, collagen fibers, the swollen macrophages. In some cases small amounts of alumina cream were still seen,
350
MANLAPAZ
ET
AL.
CAT No. II I-S L-m
P
3-s 4-m
7
A s-s CM r-. MC
c
FIG. 1. Surgical treatment. A. Control EEG recording showing mixed alpha and beta activity; B, Four weeks following alumina cream injection into left suprasylvian gyrus; note low-voltage spikes and sharp-wave activity over left parietal region. C, Immediately prior to surgical ablation; note diffuse hypersynchrony and paroxysms of spiking are present though no seizure was seen. D, Twenty-four hours after ablation; note marked flattening.
FIG.
tensive
Surgically treated alumina cream lesion in destruction of brain tissue. Loyez’ myelin stain;
2.
the x4.
brain
of a cat;
note
ex-
FOCAL
351
EPILEPSY
either lying free as globules or within macrophages. A reduction of the number of myelinated fibers with concomitant astrogliosis was usually seen in the regions surrounding the lesion, specially in the lateral gyrus. Ultrasonic Irradiation. Of the twelve animals thus treated, one died of pulmonary infection within a week of irradiation, nine were seizure-free and were killed 12 weeks later, and two had recurrences (Table 1). One of the latter developed seizures 2 days after irradiation and continued
mFoRE
I”“ADI~.IIou
24 “OURS AFTER IRRADIAImW
FIG. 3. Ultrasonic irradiation. The EEG records are comparable to those in Fig. 1; however, note that D does not show the marked flattening seen in Fig. lD, hut is comparable to the control recording shown in A.
to have occasional attacks for 4 weeks and then died of an intercurrent pulmonary infection. The other developed seizures 4 weeks after irradiation and continued to have one or two seizures a week till it was killed 12 weeks later. The EEG of the animals relieved of their seizures showed a predominance of medium- and low-voltage beta rhythm with abolition of the spike activity (Fig. 3D). An electrocorticogram of the animal with recurrence of seizures which survived for 12 weeks showed high-voltage spike activity 3 mm posterior to the site of injection of alumina cream. Pathological examination of the brains of the animals relieved of sei-
352
FIG. 4. Ultrasonically tending the left lateral
MANLAPAZ
irradiated gyrus and
ET
AL.
alumina cream lesion in the brain of a cat disthe overlying cortex. Loyez’ myelin stain; x5.5.
FIG. 5. Ultrasonically irradiated alumina cream lesion in left suprasylvian gyrus has reached the surface of the brain. Extensive destruction of neurons occurred in overlying cortex which is thin. Cresyl violet; X8.5.
FOCAL
EPILEPSY
353
zures revealed grossly a fibrotic thickening of the external surface of the dura mater at the site of the trephine hole made for injection of alumina cream. The inside of the dura and the leptomeninges were smooth and without adhesions. The surface of the gyrus was usually smooth though somewhat distended. In gross appearance these specimens did not differ from the brain of the untreated animal or those treated with medication. Microscopically (Fig. 4, 5 & 6), however, all nerve cells within
FIG. 6. Detail of alumina cream lesion in Fig. 4, showing peripheral cellular part of lesion on the right and the overlying cortex with destruction of neurons and astrogliosis on the left; the surface of the brain is at the far left. Cresyl violet; X80.
the crown of the affected gyrus had disappeared and there was usually also an extensive destruction within the other areas of the cortex adjacent to the lesion, i.e., those parts which faced the nearby sulci. Particular attention was paid to the brains of the two cats which had a recurrence of seizures after irradiation. In the first, the alumina cream lesion was found to have been incorrectly placed in the lateral gyrus instead of the suprasylvian gyrus, with the result that it had escaped ultrasonic irradiation. In the second animal the cortical destruction resulting from ultrasonic radiation was less extensive than in those animals which remained seizure-free.
3.54
MANLAPAZ
ET
AL.
Medical Treatment. Despite careful nursing, all of the nine cats treated with medication succumbed to status epilepticus 2 to 4 days after the onset of seizures (Table 1). Histological examination revealed partial neuronal damage to the overlying cortex and characteristics of the untreated lesion described above. Discussion
The incidence, time of onset and the pattern of seizures induced by subcortical application of alumina cream in cats appear to be similar to those observed in monkeys (4, 5, 10). The electroencephalographic alterations were notable in that the pathological activity was almost continuous, as was noted also by Schmalbach and Steinmann (18) in other species. The patterns of discharge during seizures resembled those seen in rabits (19) and monkeys (13, 17) with alumina cream lesions and .in post-traumatic focal epilepsy in man (9, 16). Because of this similarity and the absence of specific histochemical reactions in and around the alumina cream lesions in animals and epileptogenic foci in man, the two conditions are believed to be similar (17). The histological picture described here as well as in the extensive studies of Mayman and co-workers ( 12) would implicate partially damaged cortical neurons surrounding the alumina cream lesion in the pathogenesis of the seizures. This is further supported by the fact that the histological appearance of brains with lesions rendered quiescent by ultrasonic irradiation did not differ materially from those with active lesions except that in the former there was an almost complete destruction of neurons around the periphery of the lesion, the bulk of the alumina cream lesion itself being virtually unaffected by irradiation. We note that although the dosage of ultrasound used consistently produced lesions 15 mm long and 5 mm in diameter in the normal brain tissue (2), in this study the ultrasonically produced destruction extended barely beyond the limits of the alumina cream lesion, This is attributed to the differences in acoustical constants of the brain tissue, e.g., ultrasonic absorption coefficient, reflectance, under the two conditions. The results of this study indicate that experimental focal epilepsy and concomitant abnormal EEG patterns can be eradicated by ultrasonic irradiation with fewer postoperative complications than by current surgical techniques. The recurrence in two of the ultrasonically treated animals is ascribed to the vagaries of the free-hand injection technique employed-the alumina cream being deposited at some distance from its
FOCAL
355
EPILEPSY
intended site. That eradication of epileptogenic foci is possible with minimal damage to the surrounding brain tissue is evident from the photographs of the brains in Fig. 2, 4 and 5, as well as comparison of postoperative EEG shown in Fig. 1D and 3D. Furthermore, irradiation of an epileptogenic lesion with focused ultrasound has the advantage of being a totally extradural procedure, reducing the danger of sepsis, of subsequent formation of cortico-dural adhesions and of damage to the pia mater-all of which factors are held to contribute to the development of post-traumatic epilepsy and its recurrence after surgical ablation (9, 14). Penfield and Humphreys (15), in their histological study of the etiology of epileptogenic lesions, pointed out the detrimental role of cicatrizing vascular scars containing fibroblasts and collagen fibers, following accidental laceration of the brain. The ultrasonic lesion, on the other hand, is known to heal by gliosis and not to change appreciably in size with age (1). The studies of Chiafalo and co-workers (3) also show corticosubcortical ultrasonic lesions and scars in the precentral gyrus of monkeys to be entirely nonepileptogenic for up to 30 months. A recent editorial (6) discussing the indications for the surgical treatment of epileptogenic lesions lists the accessibility of the discharging focus as the first criterion. Green and Scheetz (8) pointed out that only 4.8 per cent of 2,500 epileptic patients satisfied indications for surgical intervention; and, furthermore, that the lesions were localized in the temporal lobe in 64 per cent of their surgically treated cases, being in the frontal, parietal or occipital areas in the remaining ones. Since it has been shown (2) that sharply circumscribed trackless lesions of any desired size can be accurately placed stereotaxically in predetermined structures anywhere within the central nervous system, without any undesired damage to other neural tissue, very few, if any, epileptogenic foci would seem to be inaccessible to eradication by the use of focused ultrasound. In treatment of post-traumatic epilepsy, the sizeable craniotomy needed for ultrasonic irradiation of deeper structures ceases to be a disadvantage and indeed turns out to be desirable, as cranioplasty is an accepted factor in the therapy of the disease (7). References 1.
ASTR~M,
perimental ultrasound 520. 2.
BASAURI,
K.
H. T. BALLANTINE, and E. HEIDENSLEBEN. 1961. An exneurophathological study of the effects of high frequency focused on the brain of the cat. J. Neuropathol. Exptl. Neurol. a0: 484-
E., E. BELL,
L., and P. P. LELE.
1962.
A simple
method
for
production
of track-
3.56
3. 4. 5.
10.
11. 12.
13.
14. 15. 16. 17.
18.
19. 20.
MANLAPAZ
ET AL.
less focal lesions with focused ultrasound: Statistical evaluation of the effects of irradiation on the central nervous system of the cat. J. Physiol. London. 160: 513-534. CHIAFALO, N., L. BASAURI, P. P. LELE, E. P. RICHARDSON, 1. GIRIUNAS, and H. T. BALLANTINE. 1964. Unpublished data. CHUSID, J. G., L. M. KOPELOFF, and N. KOPELOFF. 1955. Motor epilepsy of parietal lobe origin in the monkey. Neurology 6: 108-130. CURE, C. W., and T. RASMUSSEN. 1950. Experimental epileptogenic lesions of the cerebral motor cortex and the insular cortex in monkeys. Electroe% cephalog. Clin. Neurophysiol. 2: 354. Editorial. 1964. The surgery of epileptogenic lesions. J. Am. Med. ASSOC. 167: 671. 1963. Post-traumatic epilepsy and early ERCULEI, F., and A. E. WALKER. cranioplasty. 1. Neurosurg. 20: 10851089. 1964. Surgery of epileptogenic lesions Of GREEN, J. R., and D. G. SCHEETZ. temporal lobe. Arch. Neural. 10: 135-148. 1943. Electroencephalogram in post-traumatic JASPER, H., and W. PENFIELD. epilepsy; pre-operative and post-operative studies. Am. J. Psychiat. 100: 365377. KOPELOFF, N., J. G. CHUSID, and L. M. KOPELOFF. 1954. Epilepsy produced In Macaca Mulatta with commercial Aluminum Hydroxide. Electroencephalog. Clin. Neurophysiol. 6: 303-306. LELE, P. P. 1962. A simple method for production of trackless focal lesions with focused ultrasound: Physical factors. J. Physiol. London 160: 494-512. MAYMAN, C., J. S. MANLAPAZ, H. T. BALLANTINE, and E. P. RICHARDSON. 1964. A neuropathological study of experimental epileptogenic lesions in the cat. Unpublished data. PACELLA, B. L., N. KOPELOFF, S. E. BARRERA, and L. M. KOPELOFF. 1944. Experimental production of focal epilepsy. Trans. Am. Neuuol. Assoc. 70: 128130. PENFIELD, W. 1958. Pitfalls and success in surgical treatment of focal epilepsy. Brit. Med. J. 1: 669-672. PENFIELD, W., and S. HUMPHREYS. 1940. Epileptogenic lesions of the brain: Histologic study. A.M.A. Arch. Neural. Psychiat. 42: 240-261. PENFIELD, W., and H. H. JASPER. 1940. Electroencephalography in focal epilepsy. Trans. Am. Neurol. Assoc. 66: 209-211. POPE, A., A. MORRIS, H. JASPER, K. ELIOT, and W. PENFIELD. 1946. Histochemical and action potential studies on epileptogenic areas of cerebral cortex in man and the monkey. Res. Publ. Assoc. Res. Nervous Mental Disease 26: 218-223. SCHMALBACH, K., and H. W. STEINMAN. 1955. Bioelektrische Untersuchungen mit chronischen epileptogenen Llsionen. De&. 2’. Nervenheilkunde 173: 37?384. VISSER, S. L. 1962. The reactivity of Alumina cream foci in rabbits. Electroencephalog. Clin. Neurophysiol. 14: 747-750. YOUNG, G. F. and P. P. LELE. 1964. Lesions in the brain of rabbits at various ages produced by focused ultrasound. Bzptl. Neurol. 9: 502-511.
Effects
NEUROLOGY
of
10,
MANLAPAZ,
(1964)
Ultrasonic Focal
J. S.
345-356
K.E.
Radiation
Epilepsy
in
in the
Experimental Cat
H. T. BALLANTINE,
ASTR~M,
JR., AND P. P. LELE~
Medical Acoustics Research Group, Massachusetts General Hospital, Boston, Massachusetts Received
April
15, 1964
Introduction Experimental focal epilepsy was induced in thirty-seven cats by subcortical injection of 0.1 ml of alumina cream. Fifteen of these were treated by surgical removal of the epileptogenic focus, twelve by irradiation with focused ultrasound and nine with medication. One died before any therapy could be instituted. Ultrasonic irradiation effectively relieved the animals of the seizures and abnormal EEG patterns by eradication of the epileptogenic focus with less untoward effects and postoperative complications than did surgery. Medical therapy was ineffective. Post-mortem examination of the brains showed grossly that ultrasonic irradiation eradicated the epileptogenic focus without destroying extensively the overlying and adjacent brain tissue and without forming corticodural adhesions. Microscopically, irradiated foci could be distinguished from the surgically treated ones by inter alia absence of trabeculated loose vascular scar tissue and paucity of fibroblasts and collagen fibers. Introduction
Post-traumatic focal epilepsy is surgically treated by ablation of the focus and cranioplasty if indicated, This is not entirely satisfactory becauseof the inadequacy of control over the volume of the tissue removed (and traumatized) and the possibility of recurrence due to damageto the leptomeningesand local vasculature and the formation of corticodural adhesions (14). Focused ultrasonic radiation (11) which has been shown to be the method of choice for trackless destruction of discrete, predetermined volumes of tissue at any preselected region within the central nervous system, without any undesired damage to the other adjacent 1 This investigation was carried out under a Research Contract with of the Surgeon General, U.S. Army Medical Research and Development and supported in part by the U.S. Public Health Service. 345
the Office Command
346
MANLAPAZ
ET
AL.
tissue (2), appears to be ideally suited for treatment of focal epilepsy. The ultrasonic lesion has simple and unvarying neurophathological features (1) irrespective of the species and the age of the animal (20) and the resultant scar is of a very low epileptogenic potential (3). This study was undertaken to determine if ablation of epileptogenic foci by ultrasonic radiation transdurally is, in fact, superior to current surgical methods. For this study, experimental focal epilepsy was induced in cats by subcortical injection of alumina cream (10). Materials
and
Methods
Forty-five healthy adult cats were used. In each, under light pentobarbital anesthesia (25 mg/kg) , control electroencephalograms (EEG) were recorded from needle electrodes placed in standard positions over frontal, temporal, parietal and occipital regions bilaterally. The animal was then placed in a stereotaxic apparatus and a trephine hole 1 cm in diameter was made in the left frontoparietal region of the skull, after incision and retraction of the scalp and underlying tissues. Using a tuberculin syringe with a 22-gauge needle, 0.1 ml of alumina cream was injected slowly 2 mm below the cortical surface of either the middle suprasylvian gyrus (thirty-six cats) or the anterior sigmoid gyrus (nine cats), the former being preferred since it obviates opening of the frontal sinus which frequently leads to meningitis or respiratory infection or both. The wound was closed and the animal was then observed for abnormal motor activity for a period of 12 weeks. The EEG was recorded at weekly intervals throughout the experiment. After the first seizure, the animal was treated either surgically (fifteen cats) or by ultrasonic irradiation (twelve cats) with a dose calculated to create a lesion 15 mm long and 5 mm in diameter in normal brain (2). As a control, nine cats each were given 15 mg of sodium phenobarbital and 100 mg dilantin every day, orally when conscious or parenterally when unconscious. For surgical ablation, the previous trephine hole was enlarged under anesthesia, the dura mater was slit across the scar of the needle puncture, and the alumina cream removed by suction. The wound was closed after hemostasis. For ultrasonic irradiation, an adequate craniectomy (11) was performed and the precalculated dosage of ultrasound was delivered 2 mm below the site of injection of alumina cream. The EEG was recorded immediately after treatment and at weekly intervals thereafter for 12 weeks during which the animal was observed for seizures. It was then killed and the brain removed for subsequent
FOCAL
EPILEPSY
preparation of sections stained with H & E, cresyl violet and stain. Since subcortical application of alumina cream commonly seizures within 4 to 6 weeks (lo), animals which had not had zures or did not display an abnormal EEG till 12 weeks after of alumina cream were excluded from this study.
347
a myelin induces any seiinjection
Results
No neurological abnormality was apparent immediately following the injection of alumina cream. Of the forty-five operated animals, five died of pulmonary infection within a week of the operation. Four of the forty surviving cats (10%) developed seizures during the fourth week following the injection of alumina cream and thirty-three additional ones ( 83y0) in the succeeding 2 weeks. Three (770) showed no abnormalities for 12 weeks and were excluded from the study. The incidence or the time of onset of seizures after injection of alumina cream was not related to the site of injection, The seizures were preceded by circling, usually in a direction opposite the site of lesion, jerking of the head from side to side, followed by an audible cry; then the animal went into clonic convulsions involving the whole body. Dilatation of the pupils, fluttering of the eyelids, salivation and, on occasion, urination and defecation occurred. The convulsive phenomena lasted 15 set to 2 min and recurred every 5 to 10 min. The animal remained unconscious and flaccid after the seizure and did not regain full consciousness during the interval between the seizures. In one cat the interval between the seizures diminished, it developed epilepsia partialis continua opposite the side of the lesion and succumbed in status epilepticus before any treatment could be initiated. The EEG in the preinjection control period showed low-voltage, well organized, alpha mixed with theta rhythms (Fig. 1A & 3A). This remained unchanged after injection of alumina cream (Fig. 1B & 3B) until just prior to the onset of seizures (Fig. 1C & 3C). At this time the pattern was moderately disorganized and showed predominant beta rhythm with random paroxysmal bursts of medium- to high-voltage sharp wave and spike activity localized over the site of injection. The rest of the record was a mixture of alpha and beta rhythms. During the convulsive phase, the record became flat or nearly isoelectric in all leads for 2 to 5 min and then it reverted back to its original pattern. Pathological examination of the brains of cats which died in status
348
MANLAPAZ
ET
AL.
epilepticus showed grossly a fibrotic thickening of the external surface of the dura mater underlying the craniotomy. The inner surfaces of the dura and the leptomeningeswere smooth and without adhesions.A small rounded elevation was seen on the surface of the brain at the site of penetration of the injection needle. The surrounding areas of the same gyrus were smooth. Coronal sectioning disclosed a rounded mass of alumina cream, which had distended the gyrus and destroyed and replaced its white matter, similar to that in Fig. 4. In some instances the alumina cream was completely situated beneath the cortex which was stretched out and thinned. In other cases it had encroached upon and more or less destroyed the overlying gray matter, specially at the crown of the gyrus, as in Fig. 5. Microscopically, the lesion itself could be divided into two zones. The peripheral region consisted of a cellular granulation tissue with blood vessels, fibroblasts, rather large and free globules of alumina cream, macrophagesand a small number of inflammatory cells, e.g. lymphocytes, monocytes and plasma cells, as in Fig. 6. The center of the lesion was avascular; it seemedto contain a fluid in which a few macrophagesand alumina cream globules were suspended.The lesion was enveloped by a thin capsuleof blood vessels,frbroblasts, astrocytes and inflammatory cells. The cortex surrounding the lesion was thinned and showed extensive disorganization of cell pattern. All nerve cells had disappeared in the crown of the gyrus. There was also an extensive destruction within the other areas of the cortex adjacent to the lesion, i.e., those parts which faced the nearby sulci, where a majority of nerve cells had disappeared. Some of the remaining nerve cells appeared degenerate, dark and shrunken or very pale and frequently vacuolated. The best preserved nerve cells were found in the superficial cortical layers and the destruction appeared to increase towards the lesion. The cortex in adjacent gyri was usually well preserved, although a number of degenerated nerve cells were seen occasionally, specially in areas neighboring upon the lesion and its overlying cortex. Thus, the cortical region at the bottom of the sulci on both sides of the alumina cream mass always contained many degenerated cells and the destruction increased towards the lesion. There was an intense astrogliosis and proliferation of microglia cells within the areas of nerve cell destruction, and depopulation of nerve fibers and astrogliosis in the white matter surrounding the lesion. SurgicaZ Ablation. Six of the fifteen animals so treated died from postoperative complications (Table 1). The death was attributed to
FOCAL
349
EPILEPSY
surgical shock and cerebral edema in two and pulmonary infection in four. Eight of the nine surviving cats were relieved of seizures and remained so for 12 weeks, when they were killed. The remaining animal also was relieved of seizures after the ablation, but these recurred with reduced frequency and severity 3 weeks later. It was noted, however, that after each seizure this cat immediately regained full consciousness, shook its body and licked its fur as if nothing abnormal had happened; whereas, prior to the ablation it had failed to regain full consciousness after seizure. This cat continued to have seizures two to three times a week for 8 weeks, at which time the wound was opened for exploration with considerable difficulty due to extensive adhesions. The site of ablation was found to have been 5 mm anterior to the alumina cream lesion. TABLE NUMERICAL
RESULTS
Total number treated Died of postoperative complications Rendered seizure-free a Died
in status
OF TREAI-MENT
1 OF EXPERIMENTAL
FOCAL
Surgical
Ultrasonic
15
12
6 8
1 9
EPILEPSY Medical 9 9a 0
epilepticus.
After surgical ablation of the epileptogenic focus the EEG generally showed a predominance of low-voltage alpha rhythm with complete extinction of sharp waves and spikes (Fig. ID), except in the above animal in which paroxysmal bursts of high-voltage sharp waves and spikes were found to persist, though with reduced frequency. Pathological examination of these brains showed grossly a fibrotic thickening of the meninges with adhesions at the site of the surgical ablation. The gyrus was shrunken, the surface scarred and shriveled and its central region contained loose trabeculated and sometimes cystic scar tissue (Fig. 2). Alumina cream was seen grossly in the one animal noted above. Microscopically, the cortex overlying the lesion showed a defect which in most cases was confined to the crown of the gyrus. The adjacent areas of the cortex were fairly well preserved although many neurons showed signs of degeneration, specially in the deeper layers of the cortex, except in some cases in which it was extensively destroyed. The main part of the lesion consisted of a rather loose scar tissue which was made of astrocytes, blood vessels, fibroblasts, collagen fibers, the swollen macrophages. In some cases small amounts of alumina cream were still seen,
350
MANLAPAZ
ET
AL.
CAT No. II I-S L-m
P
3-s 4-m
7
A s-s CM r-. MC
c
FIG. 1. Surgical treatment. A. Control EEG recording showing mixed alpha and beta activity; B, Four weeks following alumina cream injection into left suprasylvian gyrus; note low-voltage spikes and sharp-wave activity over left parietal region. C, Immediately prior to surgical ablation; note diffuse hypersynchrony and paroxysms of spiking are present though no seizure was seen. D, Twenty-four hours after ablation; note marked flattening.
FIG.
tensive
Surgically treated alumina cream lesion in destruction of brain tissue. Loyez’ myelin stain;
2.
the x4.
brain
of a cat;
note
ex-
FOCAL
351
EPILEPSY
either lying free as globules or within macrophages. A reduction of the number of myelinated fibers with concomitant astrogliosis was usually seen in the regions surrounding the lesion, specially in the lateral gyrus. Ultrasonic Irradiation. Of the twelve animals thus treated, one died of pulmonary infection within a week of irradiation, nine were seizure-free and were killed 12 weeks later, and two had recurrences (Table 1). One of the latter developed seizures 2 days after irradiation and continued
mFoRE
I”“ADI~.IIou
24 “OURS AFTER IRRADIAImW
FIG. 3. Ultrasonic irradiation. The EEG records are comparable to those in Fig. 1; however, note that D does not show the marked flattening seen in Fig. lD, hut is comparable to the control recording shown in A.
to have occasional attacks for 4 weeks and then died of an intercurrent pulmonary infection. The other developed seizures 4 weeks after irradiation and continued to have one or two seizures a week till it was killed 12 weeks later. The EEG of the animals relieved of their seizures showed a predominance of medium- and low-voltage beta rhythm with abolition of the spike activity (Fig. 3D). An electrocorticogram of the animal with recurrence of seizures which survived for 12 weeks showed high-voltage spike activity 3 mm posterior to the site of injection of alumina cream. Pathological examination of the brains of the animals relieved of sei-
352
FIG. 4. Ultrasonically tending the left lateral
MANLAPAZ
irradiated gyrus and
ET
AL.
alumina cream lesion in the brain of a cat disthe overlying cortex. Loyez’ myelin stain; x5.5.
FIG. 5. Ultrasonically irradiated alumina cream lesion in left suprasylvian gyrus has reached the surface of the brain. Extensive destruction of neurons occurred in overlying cortex which is thin. Cresyl violet; X8.5.
FOCAL
EPILEPSY
353
zures revealed grossly a fibrotic thickening of the external surface of the dura mater at the site of the trephine hole made for injection of alumina cream. The inside of the dura and the leptomeninges were smooth and without adhesions. The surface of the gyrus was usually smooth though somewhat distended. In gross appearance these specimens did not differ from the brain of the untreated animal or those treated with medication. Microscopically (Fig. 4, 5 & 6), however, all nerve cells within
FIG. 6. Detail of alumina cream lesion in Fig. 4, showing peripheral cellular part of lesion on the right and the overlying cortex with destruction of neurons and astrogliosis on the left; the surface of the brain is at the far left. Cresyl violet; X80.
the crown of the affected gyrus had disappeared and there was usually also an extensive destruction within the other areas of the cortex adjacent to the lesion, i.e., those parts which faced the nearby sulci. Particular attention was paid to the brains of the two cats which had a recurrence of seizures after irradiation. In the first, the alumina cream lesion was found to have been incorrectly placed in the lateral gyrus instead of the suprasylvian gyrus, with the result that it had escaped ultrasonic irradiation. In the second animal the cortical destruction resulting from ultrasonic radiation was less extensive than in those animals which remained seizure-free.
3.54
MANLAPAZ
ET
AL.
Medical Treatment. Despite careful nursing, all of the nine cats treated with medication succumbed to status epilepticus 2 to 4 days after the onset of seizures (Table 1). Histological examination revealed partial neuronal damage to the overlying cortex and characteristics of the untreated lesion described above. Discussion
The incidence, time of onset and the pattern of seizures induced by subcortical application of alumina cream in cats appear to be similar to those observed in monkeys (4, 5, 10). The electroencephalographic alterations were notable in that the pathological activity was almost continuous, as was noted also by Schmalbach and Steinmann (18) in other species. The patterns of discharge during seizures resembled those seen in rabits (19) and monkeys (13, 17) with alumina cream lesions and .in post-traumatic focal epilepsy in man (9, 16). Because of this similarity and the absence of specific histochemical reactions in and around the alumina cream lesions in animals and epileptogenic foci in man, the two conditions are believed to be similar (17). The histological picture described here as well as in the extensive studies of Mayman and co-workers ( 12) would implicate partially damaged cortical neurons surrounding the alumina cream lesion in the pathogenesis of the seizures. This is further supported by the fact that the histological appearance of brains with lesions rendered quiescent by ultrasonic irradiation did not differ materially from those with active lesions except that in the former there was an almost complete destruction of neurons around the periphery of the lesion, the bulk of the alumina cream lesion itself being virtually unaffected by irradiation. We note that although the dosage of ultrasound used consistently produced lesions 15 mm long and 5 mm in diameter in the normal brain tissue (2), in this study the ultrasonically produced destruction extended barely beyond the limits of the alumina cream lesion, This is attributed to the differences in acoustical constants of the brain tissue, e.g., ultrasonic absorption coefficient, reflectance, under the two conditions. The results of this study indicate that experimental focal epilepsy and concomitant abnormal EEG patterns can be eradicated by ultrasonic irradiation with fewer postoperative complications than by current surgical techniques. The recurrence in two of the ultrasonically treated animals is ascribed to the vagaries of the free-hand injection technique employed-the alumina cream being deposited at some distance from its
FOCAL
355
EPILEPSY
intended site. That eradication of epileptogenic foci is possible with minimal damage to the surrounding brain tissue is evident from the photographs of the brains in Fig. 2, 4 and 5, as well as comparison of postoperative EEG shown in Fig. 1D and 3D. Furthermore, irradiation of an epileptogenic lesion with focused ultrasound has the advantage of being a totally extradural procedure, reducing the danger of sepsis, of subsequent formation of cortico-dural adhesions and of damage to the pia mater-all of which factors are held to contribute to the development of post-traumatic epilepsy and its recurrence after surgical ablation (9, 14). Penfield and Humphreys (15), in their histological study of the etiology of epileptogenic lesions, pointed out the detrimental role of cicatrizing vascular scars containing fibroblasts and collagen fibers, following accidental laceration of the brain. The ultrasonic lesion, on the other hand, is known to heal by gliosis and not to change appreciably in size with age (1). The studies of Chiafalo and co-workers (3) also show corticosubcortical ultrasonic lesions and scars in the precentral gyrus of monkeys to be entirely nonepileptogenic for up to 30 months. A recent editorial (6) discussing the indications for the surgical treatment of epileptogenic lesions lists the accessibility of the discharging focus as the first criterion. Green and Scheetz (8) pointed out that only 4.8 per cent of 2,500 epileptic patients satisfied indications for surgical intervention; and, furthermore, that the lesions were localized in the temporal lobe in 64 per cent of their surgically treated cases, being in the frontal, parietal or occipital areas in the remaining ones. Since it has been shown (2) that sharply circumscribed trackless lesions of any desired size can be accurately placed stereotaxically in predetermined structures anywhere within the central nervous system, without any undesired damage to other neural tissue, very few, if any, epileptogenic foci would seem to be inaccessible to eradication by the use of focused ultrasound. In treatment of post-traumatic epilepsy, the sizeable craniotomy needed for ultrasonic irradiation of deeper structures ceases to be a disadvantage and indeed turns out to be desirable, as cranioplasty is an accepted factor in the therapy of the disease (7). References 1.
ASTR~M,
perimental ultrasound 520. 2.
BASAURI,
K.
H. T. BALLANTINE, and E. HEIDENSLEBEN. 1961. An exneurophathological study of the effects of high frequency focused on the brain of the cat. J. Neuropathol. Exptl. Neurol. a0: 484-
E., E. BELL,
L., and P. P. LELE.
1962.
A simple
method
for
production
of track-
3.56
3. 4. 5.
10.
11. 12.
13.
14. 15. 16. 17.
18.
19. 20.
MANLAPAZ
ET AL.
less focal lesions with focused ultrasound: Statistical evaluation of the effects of irradiation on the central nervous system of the cat. J. Physiol. London. 160: 513-534. CHIAFALO, N., L. BASAURI, P. P. LELE, E. P. RICHARDSON, 1. GIRIUNAS, and H. T. BALLANTINE. 1964. Unpublished data. CHUSID, J. G., L. M. KOPELOFF, and N. KOPELOFF. 1955. Motor epilepsy of parietal lobe origin in the monkey. Neurology 6: 108-130. CURE, C. W., and T. RASMUSSEN. 1950. Experimental epileptogenic lesions of the cerebral motor cortex and the insular cortex in monkeys. Electroe% cephalog. Clin. Neurophysiol. 2: 354. Editorial. 1964. The surgery of epileptogenic lesions. J. Am. Med. ASSOC. 167: 671. 1963. Post-traumatic epilepsy and early ERCULEI, F., and A. E. WALKER. cranioplasty. 1. Neurosurg. 20: 10851089. 1964. Surgery of epileptogenic lesions Of GREEN, J. R., and D. G. SCHEETZ. temporal lobe. Arch. Neural. 10: 135-148. 1943. Electroencephalogram in post-traumatic JASPER, H., and W. PENFIELD. epilepsy; pre-operative and post-operative studies. Am. J. Psychiat. 100: 365377. KOPELOFF, N., J. G. CHUSID, and L. M. KOPELOFF. 1954. Epilepsy produced In Macaca Mulatta with commercial Aluminum Hydroxide. Electroencephalog. Clin. Neurophysiol. 6: 303-306. LELE, P. P. 1962. A simple method for production of trackless focal lesions with focused ultrasound: Physical factors. J. Physiol. London 160: 494-512. MAYMAN, C., J. S. MANLAPAZ, H. T. BALLANTINE, and E. P. RICHARDSON. 1964. A neuropathological study of experimental epileptogenic lesions in the cat. Unpublished data. PACELLA, B. L., N. KOPELOFF, S. E. BARRERA, and L. M. KOPELOFF. 1944. Experimental production of focal epilepsy. Trans. Am. Neuuol. Assoc. 70: 128130. PENFIELD, W. 1958. Pitfalls and success in surgical treatment of focal epilepsy. Brit. Med. J. 1: 669-672. PENFIELD, W., and S. HUMPHREYS. 1940. Epileptogenic lesions of the brain: Histologic study. A.M.A. Arch. Neural. Psychiat. 42: 240-261. PENFIELD, W., and H. H. JASPER. 1940. Electroencephalography in focal epilepsy. Trans. Am. Neurol. Assoc. 66: 209-211. POPE, A., A. MORRIS, H. JASPER, K. ELIOT, and W. PENFIELD. 1946. Histochemical and action potential studies on epileptogenic areas of cerebral cortex in man and the monkey. Res. Publ. Assoc. Res. Nervous Mental Disease 26: 218-223. SCHMALBACH, K., and H. W. STEINMAN. 1955. Bioelektrische Untersuchungen mit chronischen epileptogenen Llsionen. De&. 2’. Nervenheilkunde 173: 37?384. VISSER, S. L. 1962. The reactivity of Alumina cream foci in rabbits. Electroencephalog. Clin. Neurophysiol. 14: 747-750. YOUNG, G. F. and P. P. LELE. 1964. Lesions in the brain of rabbits at various ages produced by focused ultrasound. Bzptl. Neurol. 9: 502-511.