Chronic alumina temporal lobe seizures in monkeys

EXPERIMENTAL KEUROLOCY62, 99-121 (1978)

Chronic Alumina HENRY

Temporal

Lobe Seizures in Monkeys

V. SOPER, GEORGE R. JEFFREY

P. LIEB,

Braikk Rcsearclk Institute, Reed Nekcrological Surgery, U~kivrrsity Received

STRAIN, THOMAS L. BABB, AND PAUL H. CRANDALL'

APril

Nelbrological

10, 1978;

Research Cetkter,

of Califorrtia, revisiokk

Los Aikgeles, received

and Divisiork of Califortzia 90024

June 14,197s

Chronic temporal lobe seizures were induced in 11 monkeys by bilateral implantation of aluminum hydroxide into the hippocampi, With unilateral temporal lobe implants of alumina little or no epileptic activity was found; however, with bilateral alumina implants clinical seizures similar to human psychomotor attacks were initiated in either of the affected temporal lobes. Spread of alumina through the ventricles and/or tissue in some animals resulted in other seizure types, most of which could be controlled by phenobarbital, without eliminating the temporal lobe seizures. The alumina temporal lobe seizures recurred spontaneously for indefinitely long periods; however, no monkey was studied longer than 14 months. The onset of seizure activity was followed by transient anorexia and adipsia which, with large alumina volumes or other debilitating factors, could progress to fatal status epilepticus. Histology revealed that tissue reactions to the alumina included cell loss, gliosis, and neovascularization, with the most severe reaction occurring adjacent to the alumina mass. Alumina which had leaked into the ventricles in some animals reentered the brain tissue at remote sites through the choroid plexus, resulting in multiple foci.

INTRODUCTION It has been reported that of all seizure types, the complex partial seizures (psychomotor, temporal lobe, or limbic seizures) are the most resistant to anticonvulsant medication ( 13). Because these temporal lobe seizures are 1 This work was supported by National Institutes of Health Contract NS4-2331. We would like to thank Elmo Mariani, Eddie Carr, Jux Schnatmeier, and Tom Bumbera for technical assistance. Special thanks are extended to Dr. W. Jann Brown for his assistance in interpreting the tissue reactions to the alumina and to Dr. David Finch for his comments on the manuscript. Thanks are given to Sasha Biletsky for typing the manuscript and to Denise Kay, Gary Globe, Dennis Crady, and John Kiernan for their assistance during the experiments. Send reprint requests to Dr. Babb. Dr. Soper’s present address is Department of Anatomy, University of Illinois Medical Center, Chicago, Illinois 60680. 99

AI1

0014-4886/78/0621-0099$02.00/O Copyright 0 1978 by Academic Press, Inc. rights of reproduction in 8ny form reserved.

100

SOPER

ET

AL.

also the most frequently observed of all the partial or focal epilepsies (5, 13), there has been a need to develop an appropriate experimental model of psychomotor epilepsy in animals in order to test new forms of seizure control (2). Intracortical implantation of alumina (aluminum hydroxide) has been used successfully to create spontaneous focal motor seizures in monkeys which may recur indefinitely [for review see ( 17) 1. Several investigators used alumina injected into the limbic system of monkeys, or cats to study experimental temporal lobe epilepsy. This was justified by the clinical observation of extensive hippocampal and amygdaloid sclerosis in human temporal lobe epileptic patients (8). However, the details reported in those animal studies did not indicate that the seizures were chronically recurrent, spontaneous psychomotor seizures. For example, it was reported (4) that 3 to 5 weeks after alumina was implanted unilaterally into the cat amygdala, spontaneous psychomotor-like seizures occurred in 8 of 14 cats. However, these seizures were observed for only an average of 7 days (range 2 to 20 days) after their onset. Mayanagi and Walker (9) reported the occurrence of spontaneous temporal lobe seizures in only 4 of 12 monkeys with alumina implanted unilaterally in either the temporal neocortex or subcortical structures. The duration for which these temporal lobe seizures were observed was not reported. Other studies reported transient clinical seizures or fatalities after alumina implantation into various regions of the monkey limbic system (3, 10, lS>, but none provided a model of chronic temporal lobe epilepsy. The present study was designed to develop a model of psychomotor epilepsy in monkeys which would exhibit the characteristics of human psychomotor epilepsy, to trace the development and chronicity of the seizures, and to describe the histopathology of the chronic seizure focus. Our results indicate that a chronic model of spontaneous temporal lobe seizures in monkeys can be produced only with relatively large amounts of alumina distributed bilaterally in the limbic system. This technique produces spontaneously recurring complex partial seizures which may last indefinitely, but the seizure rate is variable from day to day and decreases with time. The behavior associated with these electroencephalographic (EEG) seizures also appears to change with time. In addition, excessive volumes of alumina result in spontaneous temporal lobe seizures that may irreversibly progress into status epilepticus and death. Histological examination indicates that migration of the alumina through the ventricles in some animals as well as progressive tissue reaction to the alumina may result in instability of the temporal lobe seizure focus during long periods of time, usually resulting in evidence of multifocal partial seizure syndromes.

CHRONIC

ALUMINA

TEMPORAL

LOBE

101

SEIZURES

METHODS The subjects were 11 male rhesus monkeys (Mncaca ~&utta) weighing 3.3 to 5.0 kg. All surgery was carried out under aseptic conditions and sodium pentobarbital anesthesia (35 “g/kg, intraperitoneal) . Dexameth(im) ] was used to reduce asone sodium phosphate [ (4 mg, intramuscular edema, and atropine sulfate (0.05 mg/kg subcutaneous) was used to reduce salivation. Fresh aluminum hydroxide (Amphogel, Wyeth, 64 mg/ml) was injected via stereotaxically placed cannulas into two or more TABLE Summary

Monkey

Alumina Sitea

78

79

80

81

82

of Alumina Initially

1

Implant Conditions in Monkeys Unilateral Placements

implant

Amount*

First clinical seizure (Postoperative)

Date

LAH LPH RAH RPH

0.1 0.1 0.2 0.2

4 4 21 21

Nov Nov July July

7.4 74 75 75

LAH LPH RAH RPH

0.1 0.1 0.3 0.3

7 7 18 18

Nov Nov July July

74 74 75 7.5

LAH LPH RAH RPH

0.1 0.1 0.3 0.3

5 5 25 25

Nov Nov July July

74 74 7.5 75

LAH LPH RAH RPH

0.1 0.1 0.3 0.3

5 5 24 24

Nov Nov July July

74 74 75 75

LAH LPH RAH RPH

0.1 0.1 0.2 0.2

5 5 23 23

Nov Nov July July

74 74 75 7.5

a Abbreviations: LAH, RAH-left, right posterior hippocampus. * Volume in milliliters. c Refers to most recent operation. d Clinical seizure day; days since

right

first

with

Demise (C. S. day)d and cause c

11 Dee 74 (37) 11 Aug (21)

7.5

17 Aug 7.5 (249) Status

8 4ug

75

23 Sept 76 (412) Perfused

75

15 Sept 75 (32) Asphyxiated

75

8 Sept 75 (25) Enteritis

75

5 Sept 7.5 (24) Status

(21)

14 Aug (20)

14 Aug

(21)

12 Aug

(20) anterior

observed

hippocampus;

clinical

seizure.

LPH,

RPH-left,

102

SOPER

ET

TABLE Summary

Monkey

AL.

2

of Alumina Implant Conditions in Monkeys Initially Bilateral Placements

Alumina

implant

First clinical seizure (Postoperative)

Amount”

LAH LPH RAH RPH

0.2 0.2 0.2 0.2

23 23 23 23

July July July July

75 75 75 75

13 Aug

LAH LPH RAH RPH

0.1 0.1 0.1 0.1

6 6 6 6

Nov Nov Nov Nov

75 75 75 75

12 Dee 75

33

LAH LPH RAH RPH

0.1 0.1 0.1 0.1

7 7 7 7

Nov Nov Nov Nov

75 75 75 75

10 Dee 75 (33)

30A

LAH LPH RAH RMH RPH

0.1 0.1 0.1 0.1 0.1

2 2 2 2 2

Nov Nov Nov Nov Nov

77 77 77 77 77

6 Jan 78

LAH LPH RAH RPH

0.1 0.1 0.1 0.1

13 13 13 13

Feb Feb Feb Feb

78 78 78 78

14 Mar

LAH LPH RAH RPH

0.1 0.1 0.1 0.1

15 15 15 15

Feb 78 Feb 78 Feb 78 Feb 78

11 Mar (24)

32

40

49

a Abbreviations: RMH-right in Table 1. b Volume in milliliters. c Clinical seizure day; days

Date

Demise (C. S. day)c and cause

Sitea

30

middle

since first

with

75

10 Ott

(21)

(36)

75 (58) Status

27 Feb 76 (77) Perfused

8 Feb 77 (426) Perfused

Still

alive

Still

alive

(65)

78

(29)

hippocampus;

observed

clinical

78

other

13 Mar 78 (2) Status-killed

abbreviations

as given

seizure.

of the following temporal lobe sites: anterior (A 9.0, L 10.1, H -4.O), middle (A 6.0, L 10.1, H -1.9), or posterior (A3.0, L 10.7, H 0.2) hippocampus (14). Injection volumes ranged from 0.1 to 0.3 ml. Location and volume of injections for each monkey are summarized in Tables 1 and 2.

CHRONIC

ALUMINA

TEMPORAL

LOBE

SEIZURES

103

Alumina placements in unilateral hippocampus and bilateral hippocampus were studied. Bipolar stainless-steel depth electrodes were stereotaxically placed bilaterally in anterior and posterior hippocampus, in or adjacent to the alumina injection sites. Stainless-steel screws (6.4-mm diameter, No. 4 self-tapping) for cortical EEG recordings were placed bilaterally in the calvarium over the motor (A 14.0, L tlO.O), frontal (A 25.0, L + I&O), central (A 6.0, L -t-20.0), and parietal (P 13.0, L -+1&O) cortices. After surgery the animals recovered in their home cages. Prophylactic antibiotic therapy, both systemic (cephazolin sodium 165 “g/day, im) and topical (Polysporin ointment), was administered for 1 week postoperatively and afterwards as needed. Transient postoperative anorexia and adipsia, when present, were treated with intramuscular injections of vitamin supplements, and Nutrament by oral syringe or nasogastric tube. Animals whose seizure activity developed into status epilepticus were treated with vitamin supplements, oral or nasogastric feedings, and aggressive anticonvulsant drug therapy. After experimenting with several drugs used in the treatment of temporal lobe epilepsy in humans (carbamazepine, phenytoin, diazepam, phenobarbital) a standard therapy was developed, consisting of an initial single injection of diazepam, 2 to 6 mg, im, followed by phenobarbital, 20 to 40 mg, im, twice a day until the seizure activity had stabilized. Serum phenobarbital levels were measured by gas-liquid chromatography (University of California, Los Angeles Clinical Laboratories). The development of seizure activity was followed both behaviorally and electrophysiologically, including split-screen videotape analysis of the relation between EEG paroxysmal activity and seizure behavior. During recording sessions the EEG was recorded on paper and/or on FM magnetic tape. In addition, the amplified signal was fed through an EEG seizure detecting circuit (1). All such records were retained for analysis and computation of EEG seizure rate, duration, and interictal intervals. Split-screen videotape recordings of concurrent EEG and behavior allowed a more accurate categorization of the seizure types exhibited by monkeys with chronic alumina foci, and permitted observation of changes in EEG and behavioral seizure patterns with time. Animals were killed under sodium pentobarbital anesthesia. The brains were perfused with heparinized normal saline followed by 10% formalin, and were frozen or embedded in paraffin. Coronal sections were taken through the hippocampi as well as through any regions with obvious damage caused by the alumina cream injections. The sections were stained with thionin or cresyl violet and examined microscopically to determine the extent of damage. Reconstructions of the loci of the alumina at the time of death were plotted from projected enlargements of the sections. Brains of

1WJV

FIG. 1. A representative subclinical EEG seizure recorded from monkey 80 after bilateral alumina placement. The epileptic activity was restricted to the left hippocampus and was followed by a clear postictal depression. In Part B (continuous with Part A) there appeared to be a slight projection of the epileptic activity to the right hippocampus and motor cortex, but without postictal depression. LT.ANT.HIP-left anterior hippocampus.

CHRONIC

ALUMINA

TEMPORAL

LOBE

SEIZURES

animals which died while the experiment was in progress were much as possible by immersion before histological processing.

105 fixed as

RESULTS Electvoplzysiology aud CliGcal Symptowatology. Two anatomical patterns of alumina placement were studied: unilateral hippocampus and bilateral hippocampus. U?zilateraZ hippocamps. Alumina placement of 0.1 ml in the left anterior and posterior hippocampus in five animals (monkeys 75 through 8.2)) summarized in Table 1, was followed in 5 weeks by a transient period of anorexia and adipsia lasting 1 to 2 weeks. Behavioral observations of these five animals for 5 to 12 h a day, 5 days a week for 6 months resulted in detection of clinical seizure activity in only one animal (monkey 78). The seizures, occurring once each on postoperative Days 37, 39, 71, and 79, consisted of a stereotyped behavioral pattern: mastication, followed by a rotation of the head to the right with exaggerated blinking, more severe on the right, followed by spread of the clonic movements to the upper extremities. During the first seizure the animal was unresponsive to external stimulation, but during the later seizures it did not appear to lose consciousness. The clinical symptoms lasted approximately 1 min. No other seizure activity was observed during the 6-month observation period. Bilateral hifipocanzpus. When chronic seizure activity failed to develop in monkeys 78 through 82, additional implants of either 0.2 or 0.3 ml alumina were made in the contralateral homologs (see Table 1). In addition, bilateral hippocampal placements were made in six monkeys (Table 2). Subclinical electroencephalographic seizure activity began to appear about 2.5 weeks after the second implant in monkeys 78 through 82. The epileptic EEG activity was restricted to one hippocampus, with little or no involvement of the cerebral cortex or contralateral hippocampus. The seizure activity usually began in the old focus (left hippocampus) as in Fig. 1, but occasionally was instead observed in the right hippocampus. Postictal depression was often seen in the brain regions involved in the seizure. Clinical seizure activity began to appear about 3 weeks after the second implants, typically consisting of an upward deviation of the head to the right, followed by eye-blinking (more intense on the right side), mastication, salivation, and myoclonic jerking of the right arm. This seizure activity could be inhibited with diazepam, 5.0 mg, im, for periods as long as 2 11. Electrographically the seizures were initially similar to the pattern seen with subclinical seizure recordings, Fig. ZA, B. However, spread to the contralateral hippocampus, as in Fig. 2C, D, coincided with the

106

SOPER

ET

AL.

(a pue -J s)rQ) a$oN sndumodd!q

MOO1

sL3nv ST 3 VJW

h

'%+-

OS ‘NNOW

xl3lOlOW

dlHlSOd'l1

dlHlSOd'lU dlH'l.NV'l.M

dlHlSOd'UJ dlH ‘INV '11 dlHlSOd*l~

*amzras .xo$otuoyxGd p~~o!mqaq aq~ ~J!M Bu!pyqo3 ‘xavo~ ~o$our pue sndumoddg $qB!.I aql o$ b[asua~ur pealds dIp3I$uaaa a.mz!as aq$ $nq ‘1 ‘%A JO asoq$ 0~ .nq!ru!s a-m g pUE V Wed u! sulawd 3x3 aql Wql $faI aq$ ut .8uyx@~o a.mz!as px+!~3 1: %u!Jnp 1 ‘B!d se bep aLueS aq? UO 08 daqUOLU luo~f s8UpJO~a~ ‘Z 31s

WIIZBSlV9lNil3

108

SOPER

ET

AL.

A similar relationship between clinical initiation of clinical symptoms. seizures and contralateral propagation of limbic seizure activity has been reported in human temporal lobe epileptic patients (7). After another 2 weeks, three of the animals lapsed into a state of nearly continuous, mild clinical seizures (epilepsia partialis continua) with continuous interictal spiking. A regimen of anticonvulsant and amino acid replacement therapies with force-feeding was instituted ; however two (75 and 82) did not respond, and died. The third monkey (SO) died from regurgitation and asphyxiation during a seizure, shortly after being forcefed. The other two monkeys with second alumina implants recovered from the anorexia associated with the onset of clinical seizures, and continued to have several psychomotor seizures per day. Monkey 81 died of an unrelated cause (telescoped colon), while monkey 79 was maintained until killed 432 days after the second alumina implant. The first animal with bilateral hippocampal alumina (0.2 ml in each of four sites) implanted on one operation (monkey 30) also entered epilepticus partialis continua but responded to phenobarbital (2.9 mg % serum levels), and was maintained on 60 mg im/day for 2 months before it died. Because of the high mortality seen with large alumina injections, subsequent placements were kept to 0.1 ml/site, with additional sites added as necessary. The development of the focus in two animals (monkeys 32 and 33) receiving 0.1 ml alumina cream at each of four sites (anterior and posterior left and right hippocampi) was followed closely electrographically, and will be reported in detail as typical of the remaining animals in this group. Epileptiform EEG activity was first evident in monkey 33 on postoperative Day 26, when abnormal slow waves and spikes every 20 s appeared in the left hippocampus. This rate of spiking increased 12-fold over the next 5 days. On Postoperative Day 33 the animal was observed having cIinica1 seizures consisting of head-turning to the right, lip-smacking, and mastication. The animal was usually conscious during these episodes and the EEG generally exhibited postictal depression. Electrographically the seizure activity appeared to be initiated from the hippocampus (Fig. 3), although the side of the initiation was not always clear. These episodes always spread bilaterally and invaded the cortex. The seizures lasted about 2 min and occurred approximately twice per hour. During the next 2 days the seizure rate increased to about 9/h, so the animal was placed on a regimen of 1 mg im diazepam bid and 20 mg im phenobarbital bid. The following 3 days (to Day 38) the seizure frequency remained unchanged while the duration increased to as long as 8 min. The seizures became nearly continuous, with one side appearing to trigger the other in a continuously alternating fashion. There was no stable background

DAY 33

FIG. 3. EEG tracings of the first clinical seizure recorded from monkey 33 on day 33 after the bilateral alumina implants. Note that the seizure originated in the left anterior hippocampus and spread more rapidly to the right anterior hippocampus than to either posterior hippocampus. Motor cortex involvement did not occur until several seconds later, when the observed psychomotor attack was well underway.

10 DEC. 7s. POST-OP.

CI z

110

SOPER

Range

Dates

of Average Serum

Daily Seizure Phenobarbital Frequency (seizures/h)

ET

At.

Frequencies and Levels in Monkey

Durations 33

Duration (min)

and

Modal serum phenobarbital (mg

12/75-l/76 2/76-3/76 7/76-S/76 l/77-2/77

l.O-status 1.7-12.2 3.1- 6.2 3.6- 6.6

1.3status l.O- 2.6 4.3-14.2 1.9- 2.0

%I

2.8 2.8 1.0 0.0

activity visible in the hippocampal recordings and there was continuous abnormal slowing in the motor cortex. The animal was not responsive during most of these seizures. The animal’s condition further deteriorated the next 4 days to a state of lethargy, apparent exhaustion, and general unresponsiveness to external stimulation. On Day 43 the animal was found lying on the bottom of its cage and by Day 45 there was almost continuous seizure activity in the motor cortex (status epilepticus). However, with continued anticonvulsant therapy the animal’s seizure frequency was reduced to a manageable level. During the next 14 months the general condition of monkey 33 improved to the point that it was no longer necessary to continue the anticonvulsant drugs (Table 3), although the seizures remained chronic. This probably resulted from a long-term change in the effectiveness of the focus, which was found by others in a much shorter term (15). During the 426 days that monkey 33 exhibited spontaneous seizures, the seizure types changed. For approximately 6 months nearly all seizures originated with EEG seizure patterns in the hippocampus, but eventually clinical seizures were observed where there was initial EEG seizure activity in the parietal or motor cortex. This “spread” of epileptic foci was probably due to spread of the alumina away from the hippocampus to other regions (see histopathology section), such as the thalamus, and these new foci became active when phenobarbital medication was withdrawn (Table 3). Figure 4 shows a seizure which originated simultaneously in the cortex and left anterior hippocampus. At this time (Postoperative Day 403) the serum phenobarbital was zero. Other generalized seizures were recorded on split-screen videotape and showed that with certain seizures the behavioral seizure activity preceded the EEG seizure activity recorded from either left or right hippocampus, or parietal or motor cortex. Such seizures must have been initiated from some region, e.g., the thalamus, where recording electrodes had not been placed. Nevertheless, even after 372 days

FIG. 4. EEG tracing of a clinical seizure recorded from monkey 33, 403 days after alumina implant. Note that the EEG seizure originated simultaneously in the left anterior hippocampus and motor cortex and then spread to other regions.

CONT.

z +

.,..

.

.

..

”

.

.*\

.

.-,.

r

,

-

..,

,

..,W..P,

.

..-

I./

.

.

.._.

.

.

.

._I,

___,.,

,_.

.

...,.

FIG. 5. EEG tracing of a clinical seizure recorded from monkey 33, 405 days after alumina tensity of the EEG seizure activity was not as great as 1 year previously (see Fig. 3), the campus (end of second set of tracings) before spreading to other regions of the hippocampus behavior was a typical psychomotor attack.

__

.

.

,.-

.__.

.

-

.

.._...q-

implants. Note that although the inonset still occurred in the left hippoand motor cortex. The concomitant

.

CHRONIC

ALUhIINA

TEhfI’ORAL

LORE

SEIZURES

FIG. 6. Reconstructions of the sitesof alumina (stippledoutlines) in the brain of monkey 80. Note that there was aluminathroughout the right lateral ventricle, 32 days after 0.3 ml was implantedin the anterior and posterior right hippocampus. However, there was virtuallg no aluminadetectablein the left hemisphere, 314 days after 0.1ml of aluminawas implantedin the left anterior and posteriorhippocampus. Coronalsectionson the right are front views, thus left and right are reversed.

of spontaneous seizures, partial complex seizures originating in the hippocampus were commonly observed. Monkey 33 continued to have such temporal lobe seizures (see Fig. 5) until it n-as killed for histological studies on Postoperative Day 459. The development of the focus in monkey 32 resembled that of monkey 33 except that this animal did not develop either type of status condition. On Day 32 the EEG displayed a suppressionof fast activity with abnormal slowing in the left depth leads. Two days later the slowing in depth was bilateral and spikes appeared in the right anterior hippocampus at about once every 20 s. At this time the animal also began having 1-min clinical seizures once an hour. Electrophysiologically they were initiated in the right hippocampus, propagating to the left hippocampus and then to motor cortex. Two days later (postoperative day 36) the seizures had increased to four per hour and a duration of about 2 miu, at which time a regimen

114

SOPER

ET

AL.

FIG. 7. Reconstructions of the sites of alumina (stippled outlines) in the brain of monkey 32. Note that there was roughly the same amount of alumina present in each hemisphere 113 days after 0.1 ml of alumina was implanted bilaterally in the anterior and posterior hippocampus. Coronal sections are front views.

of 20 mg im phenobarbital per day was initiated. At this dosage the activity was reduced to only occasional clinical seizures, so on Day 70 the animal was taken off the medication. It continued to have only one or two seizures a day until killed 113 days after the bilateral alumina cream implantation. The remaining three animals also developed psychomotor seizures. Two (30A and 40 remain alive and healthy without requiring anticonvulsant medication. The third (49 went into status over a weekend and sustained extensive anoxic brain damage before anticonvulsant therapy could be instituted, so it was killed. Histopathology of the Chronic AlatmninaFocus. Figures 6 and 7 are representative reconstructions of the locations of alumina 1, 4, and 10 months after implantation in the ventral hippocampi (see Tables 1 and 2 for implant conditions. In some monkeys the alumina entered the ventricles surrounding the hippocampi and migrated dorsally (e.g., monkey 80 in Fig. 6). Alumina particles were found as far away from the hippocampus as the third ventricle. Such ventricular spread of alumina was also reported by Gastaut et al. (4) and Mayanagi and Walker (9). In a few monkeys the presence of alumina in the thalamus may have been due to spread of

CHRONIC

ALUMINA

TEMPORAL

LOBE

SEIZURES

115

the alumina through tissue with time. Microscopic examination of the choroid plexus adjacent to a mass of alumina in the ventricle suggested that alumina that had leaked into the ventricle might have reentered the brain in small amounts. For example, Fig. 8 shows photomicrographs of alumina in the dorsal and ventral portions of the lateral ventricle of monkey 80. The lower left photomicrograph (right hippocampus) shows the apposition of the alumina mass and the hippocampus, where alumina particles have passed through the choroid. Similarly, in the dorsal ventricle, alumina penetrated the choroid and entered periventricular limbic regions. Hippocampal lesions need not be adjacent to a mass of alumina, as is shown in Fig. 8. The lower right photomicrograph shows extensive cell loss, gliosis, and neovascularization in the left ventral hippocampus in the absence of large amounts of alumina. This left hippocampal lesion may have resulted from reaction to alumina implanted there 11 months earlier or possibly also may have been due to ischemic cell loss following the recurrent major motor seizures occurring after the right-side alumina implant. It is not known how the alumina leaves the parenchyma; however the evidence suggests that the amount of detectable alumina decreases with time. For example, there is little alumina remaining 11 months after implantation into the left hippocampus of monkey 80 (Fig. 6). By contrast alumina remained in the brain of monkey 32 113 days after implantation (see Fig. 7). There was an intense, complex tissue reaction to the alumina. In monkey 32, which was killed 113 days after bilateral alumina implants and after 77 days of temporal lobe seizures, a wide range of tissue pathology was found. Figure 9 shows that in the right hippocampus (lower left photomicrograph) there was severe cell loss, gliosis, and neovascularization, whereas at the same level the opposite hippocampus was virtually normal (lower right photomicrograph). However, at a more posterior level the left hippocampus exhibited damage similar to that shown in the right hippocampus. The most severe tissue reaction always occurred adjacent to a mass of alumina. The upper right photomicrograph of Fig. 9 shows that the abscess, in this figure shown in the lateral geniculate, was surrounded by a granule reaction consisting of macrophages, fibroblasts, and patent vessels, This granule was bounded by a gliotic reaction consisting primarily of astrocytes, most of which contained calcified alumina, Alumina was also found in macrophages. Similar descriptions of tissue reaction to alumina were reported elsewhere (6, 9). DISCUSSION The data presented demonstrate that it is possible to induce a chronic state of temporal lobe epilepsy in monkys in which spontaneous clinical

116

SOI’ER

ET

AL.

CHRONIC

ALUMINA

TEMPORAL

LOBE

SEIZURES

117

seizures occur with their electrographic origin in the deep temporal lobe. This is the first technique to produce a true chronic model of temporal lobe epilepsy. These seizures, furthermore, are partial seizures in which motor involvement may be limited and of relatively short duration. The clinical signs of the temporal lobe seizure may consist of any combination or series of behaviors ranging from absence, head-turning, mastication, salivation, upper extremity movements, to clonic movements of the whole body. However, the intensity of the movements is clearly lower and shorter than that associated with major motor seizures which have a generalized electroencephalographic onset. In some cases there was either a mixed seizure pattern, probably resulting from the eventual spread of alumina which created additional epileptic foci, or partial seizures which on certain occasions generalized into major motor seizures. These other seizures could usually be controlled by anticonvulsant medication without fully controlling the occurrence of the temporal lobe seizures. In this regard the alumina model of temporal lobe epilepsy was very similar to intractable psychomotor epilepsy in man, where anticonvulsant therapies prevent generalized motor seizures but poorly control the psychomotor attacks (13, 16). The difficulty in establishing a good model of temporal lobe epilepsy in monkeys by the use of intracerebral aluminum hydroxide is evident in our report of several fatalities (4 of 11) and in the need for multiple-site implants in all 11 monkeys. It should be noted, however, that three of the four fatalities occurred in animals receiving large total volumes of alumina (0.6 to 0.8 ml) and large volumes of alumina per injection site (0.2 to 0.3 ml), with a greater resultant possibility of extensive ventricular spread and intractable multiple focus disorders. Postmortem examination of the fourth animal (49) revealed liver cirrhosis, a massive fecal impaction with necrotic lesions, and weight loss, which would have significantly reduced the monkey’s resistance to the debilitating effects of a high seizure frequency. Our results suggest that to establish a chronic, spontaneously recurring seizure state, alumina lesions must be created in a large portion of both hippocampi by multiple, small-volume injections. The exact amount of tissue and/or the particular limbic regions which must be affected by the FIG. 8. Photomicrographs from monkey 80 showing the hippocampal pathology resulting from the alumina implant (coronal section, front view). The top photo shows that alumina spread dorsally within the right ventricle (compare with Fig. 5). This monkey had both psychomotor and major motor seizures, and some of the cell loss may have been due to anoxic episodes. However, there was clearly a decrease in the number of hippocampal pyramidal cells bilaterally. The lower right photo of the left hippocampus (X19) shows extensive gliosis throughout the hippocampus and neovascularization most prominent in CA4. The lower left photo of the right hippocampus (X19) shows there was alumina in the ventricle and adhering to the choroid. Note the lack of pyramidal cells in the adjacent region of the hippocampus.

118

SOPER

ET

AL.

CHRONIC

ALUMINA

TEMPORAL

LOBE

SEIZURES

119

alumina cannot be determined on the basis of our limited number of epileptic monkeys. It is not clear from our results whether it is preferable to create several limbic foci in one operation or in several stages separated in time. However, our results tend to suggest that bilateral implants are more important than the total amount of alumina implanted on one side. Also, the amount of alumina that remains in tissue and does not leak into the ventricles may be very important. Such migration of alumina was evident in some of our implants and was also reported by others (4, 9). For this reason, stereotaxic placement in hippocampal sites equidistant from all ventricular borders is important. The observation in this study that bilatrral implants of alumina into the temporal lobes were necessary to produce chronically recurring seizures suggeststhe existence of mutual facilitation between left and right temporal lobe epileptic foci. It was shown (11) with estrogen foci in the cat sigmoid gyrus that asymmetrically placed contralateral foci markedly facilitated the epileptic activity through cortical-subcortical-cortical pathways. However, weaker callosal inhibitory mechanisms were also seen to interact with the dominant facilitatory effects. Inhibitory callosal influences also were demonstrated in neocortical alumina foci in monkeys (12). Thus the seizure activity in one hippocampus may be affected by the presenceof contralateral epileptic foci. Our results suggest that such influences are predominantly facilitatory, but further studies are necessary. There was some evidence of dominant epileptic foci with bilateral hippocampal alumina placements, but seizure onsets could alternately occur on both sides in those monkeys receiving two-stage implants. Bilaterally synchronous seizure onsets were also seen occasionally, but this was more apparent with older, well-established bilateral foci. Finally, it became apparent that new foci could develop in someanimals long after the alumina implants, presumably due to spread of the alumina through ventricles and/or tissue. Although the temporal lobe foci continued to generate psychomotor-like seizures, other behavioral seizures were observed where it was not possible to detect the region of electrographic seizure onset. FIG. 9. Photomicrographs of the brain of monkey 32 showing the tissue reaction to the alumina (coronal section, front view). This monkey had primarily psychomotor seizures and received phenobarbital for 1 month to prevent major motor seizures. Note that there was severe damage to the right hippocampus (lower left photo, X10) but the left hippocampus (lower right photo, X8) remained almost normal. However dt more posterior portions of the left hippocampus alumina was present in the hippocampus proper (see Fig. 6) and there was a severe necrotic reaction similar to that shown in the upper right photo (X19). The abscess necrosis was bounded by a granular wall consisting of macrophages, fibroblasts, and patent vessels. Next to the granule was a gliotic reactiqn primarily involving astrocytes.

120

SOPER ET AL.

With these seizures, either the EEG seizure onset was recorded simultaneously in hippocampus and in cortex just prior to the behavioral seizure, or in one instance the behavioral seizure monitored on split-screen videotape preceded any detectable EEG seizure patterns. The development of new foci or the presence of generalized seizure onsetswas accompanied by an apparent decreasein the daily rate of clinical seizures (see Table 3). However, this was well quantified in only one monkey (number 33), whose seizures were monitored for 14 months. During that period the intensity of the temporal lobe seizures increased and then decreased, but never disappeared completely. The increases and decreaseswere variable from day to day, but over periods of 2 months the weekly average rate was stable enough in these animals to allow studies of experimental treatments on seizure rate. Further studies of the longterm variabilities in temporal lobe seizures are currently underway. REFERENCES 1. BABB, T. L., E. MARIANI, AND P. H. CRANDALL. 1974. An electronic detection of EEG seizures recorded with implanted electrodes. cephalog. C&z. Neurophysiol. 37 : 305-308. 2. BABB, T. L., H. V. SOPER, J. P. LIEB, W. J. BROWN, CRANDALL. 1977. Electrophysiological studies of long

3. 4.

5. 6. 7.

8.

9. 10.

11.

circuit for Electroen-

C. A. OTTINO, AND P. H. term electrical stimulation of the cerebellum in monkeys. J. Ncurosurg. 47 : 353-365. DAVID, J., AND R. S. GREWAL. 1976. Effect of carbamazepine (TegretoF) on seizure and EEG patterns in monkeys with alumina-induced focal motor and hippocampal foci. Efiilepsiu 17 : 415-422. GASTAUT, H., A. MEYER, R. NAQUET, AND J. D. CAVANAGH. 1959. Experimental psychomotor epilepsy in the cat : electro-clinical and anatomo-pathological correlations. J. Neuropathol. Exp. Neural. 18 : 270-292. GASTAUT, H., J. L. GASTAUT, G. E. GONCALVES E SILVA, AND G. R. SANCHEZ. 1975. Relative frequency of different types of epilepsy employing the classification of the International League Against Epilepsy. Epilepsia 16 : 457-461. HARRIS, A. B. 1975. Cortical neuroglia in experimental epilepsy. Exp. Neural. 49 : 691-715. LIEB, J. P., G. 0. WALSH, T. L. BABB, R. D. WALTER, AND P. H. CRANDALL. 1976. A comparison of EEG seizure patterns recorded with surface and depth electrodes in patients with temporal lobe epilepsy. Epilepsia 17: 137-160. MARGERISON, J. H., AND J. A. N. CORSELLIS. 1966. Epilepsy and the temporal lobes. Brain 89 : 499-530. MAYANAGI, Y., AND A. E. WALKER. 1974. Experimental temporal lobe epilepsy. Brain 97 : 423-446. MORRELL, F., L. ROBERTS, AND H. H. JASPER. 1956. Effect of focal epileptogenic lesions and their ablation upon conditional electrical responses of the brain in the monkey. Electroencephalogr. Clin. Neurophysiol. 8 : 217-236. MUTANI, R., L. BERGAMINI, R. FARIELLO, AND G. QUATTROCOLO. 1972. An experimental investigation on the mechanisms of interaction of asymmetrical acute epileptic foci. Epilepsia 13 : 597-608.

CHRONIC

ALUMINA

TEMPORAL

LOBE

SEIZURES

121

12. NIE, V., J. J. MACCABE, G. ETTLINGER, AND M. V. DRIVER. 1974.The development of secondary epileptic discharges in the rhesus monkey after commissure section. Electroencephalogr. Clin. Neuropkysiol. 37 : 473-481. 13. PENRY, J. K. 1975. Perspectives in complex partial seizures. Pages l-14 in J. K. PENRY AND D. D. DALY, Eds., Complex Partial Sci~urcs and their Treatmmt. Raven, New York. 14. SNIDER, R. S., AND J. C. LEE. 1961. A Stcreotn.ric -4tla.s of the Monkey Brais. Univ. Chicago Press, Chicago. 15. VELASCO, M., F. VELASCO, F. ESTRADA-VILLANEUVA, AND A. OLVERA, 1973. Alumina cream-induced focal motor epilepsy in cats. Part 1 : lesion size and temporal course. Epilepsia 14 : 3-14. 16. WALTER, R. D. 1973. Tactical considerations leading to surgical treatment of limbic epilepsy. Pages 99-119 in M. A. B. BRAZIER, Ed., Epilepsy, Its Pherzomelra ilz Ma% Academic Press, New York. 17. WARD, JR., A. A. 1972. Topical convulsant metals. Pages 14-35 in PUHPURA et al., Eds., Experinzextal Models of Epilepsy. Raven, New York. 18. YOUMANS, J. R. 1956. Experimental production of seizures in the Macaque by temporal lobe lesions. Nczrrology (Mirzrteapolis) 6 : 179-186.