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Sequelae of sural nerve biopsies
Sequelae of sural nerve biopsies R. Poburski*, J.-P. Malin*, and E. Stark*
Introduction
Summary
Nerve biopsies are usually carried out as a diagnostic routine procedure in polyneuropathies and degenerative conditions of the nervous system1-5. The histological examination provides information on involvement of the peripheral neuron in the pathologic process. But only in a few conditions a specific diagnosis can be made on the basis of the histological findings (e.g. STARK und B6HM6). Generally dteI?itiOnS Of peripheral nerves such as demyelination or axonal degeneration may have a variety of aetiologies. In so far the value of this method for clinical purposes is limited, whereas for research it still is extremely helpfu12. Different nerves had been chosen for biopsy in the past. According to the recommendations of DYCK and LOFGREN' most authors have come to prefer the sural nerve at ankle level. It has no motor fibres so that biopsy cannot give rise to a motor deficit. Because of its superficial location above the deep muscle fascia and adjacent to the lesser saphenous vein the nerve is easily accessible*. At the ankle region the whole nerve can be removed over a length of 3 to 8 cm. In order to minimize subsequent loss of sensation some authors remove only a few fascicles by microsurgery and preserve the continuity of the nerve trunk. Biopsies of peripheral nerves are often referred to as minor operations with no conse*Neurologische
Klinik der Medirinischen
Sequelae of sural nerve biopsy were examined in 24 patients. Fourteen subjects reported persisting pain or dysaesthesias for more than one year. In nine patients the symptoms were mild, in five severe. Hypaesthesia of the lateral aspect of the foot was found in 17 out of 18 patients with otherwise normal or only slightly impaired sensory function. In one patient sural nerve biopsy did not cause permanent sensory loss. Pain and dysaesthesia were not significantly related to post-biopsy or generalized hypaesthesia. Key words: Sural nerve biopsy, follow-up examination, sequelae
quences other than mild sensory 10s~‘~~.On the other hand it is well known that even minor injuries of distal branches of the median nerve can cause painful burning sensations resembling causalgialOJ1. These sensations are triggered by pressure or cold. Furthermore patients may complain of dysaesthesias in the sensory area of the damaged nerve induced again by tactile or thermic stimuli. The proximal parts of completely seperated nerves may transform into neuromas, which tend to be extremely tender to touch or pressure. As the sural nerve biopsy is a merely diagnostic procedure, it is important to know, whether or not it may give rise to troublesome symptoms
Hochschule Hannover (Direktor: Prof. Dr. H. Schliack)
Address for correspondence and reprint requests: J.-P. Malin, Neurologische Konstanty-Gutschow-Strasse 8, 3ooO Hannover 61, FRG. Accepted
Klinik der Medizinischen Hochschule Hannover,
11.6.85
Clin Neurol Neurosurg 1985. Vol. 87-3.
193
other than loss of sensation. We report a followup study of 24 patients, who had undergone sural nerve biopsy more than one year earlier.
Table
1. Diagnosis
of biopsied
patients
;-----c;
Patients and method. In a four years period (1979-1983) 82 biopsies in neurologic patients had been carried out for diagnosis of peripheral neuropathies and metabolic or degenerative diseases of the nervous system. The biopsy had been taken at ankle level under local anaesthesia. lo-20 ml lidocaine 1% was injected subcutaneously from just behind the distal malleolus to about 8 cm proximally. The incision was made along the course of the lesser saphenous vein over a length of 5 to 8 cm. After retraction of the vein the sural nerve could be removed. It was divided first proximally with a scalpel to render the distal cut painless. The nerve stumps needed no further treatment. The biopsy specimen was immediately immerged in fixation fluid. After hemostasis the skin was reapproximated and a dry dressing was applied. Usually the patients were immobilized for 24 hours. All patients received an invitation to come to a follow-up examination, to which 24 (29%) appeared. They were aged 20 to 71 years (mean 47, median 43.4), and biopsy was done 1 to 4 years before (mean to 2.1, median 2 years). All patients had a full neurological examination. The extension of sensory deficit in the sural nerve territory was assessed by pinprick, marked on the foot, and copied on transparent plastic sheets. The area was measured by a computerized digitizer (ZEISS IBAS I). Sensory loss relative to body surface was computed. Sensitivity for light touch, temperature and vibration were not evaluated, as most patients were not able to localize deficits of these modalities exactly on repeated trials, whereas the extension of hypalgesia could be determined with sufficient reliability. The biopsy incision site and the denervated area were palpated for hyperalgesia and evidence of neuroma. Primary disease: 18 patients (75%) suffered from polyneuropathies which in 3 cases were caused by diabetes mellitus and in 4 cases by immunological diseases. 7 subjects had neuronal atrophies. In 4 cases the aetiology was unknown. 9 patients had 194
considerable hypaesthesia in both lower legs due to the neuropathies. In 8 patients biopsies were done for evaluation of other systemic disorders of the nervous system, which did not exclusively affect the peripheral neuron (Table 1). One subject was finally diagnosed to have a myopathy. Results Loss of sensation
Although the sural nerve had been completely separated in all individuals, sensory deficits had a wide intra-individual range. It has a mean extension of 45,7 cm* (range 10.8 to 99.6) corresponding to 0.27% of the body surface (range .06 to .37). In some cases hypalgesia was confined to a circular area with a diameter of about 3 cm distal the lateral malleolus. One woman with normal function of peripheral neurons had no loss of sensation at all. In 5 patients with severe neuropathic hypaesthesia in both lower legs no additional sensory impairment resulting from biopsy could be determined. One deafmute patient was unable to cooperate, when sensory functions were examined. Most patients reported that the area of numbness had been larger immediately after biopsy. Discomfort 14 out of 24 patients
(58%) had more or less severe discomfort in the sural nerve territory. They reported different kinds of paraesthesias or aching pain (Table 2). Three subjects considered the hypalgesia itself as troublesome. Table
2. Complaints
at follow-up*
electric shoe-like sensation ‘prickling’ on touch or pressure burning pain, brought on by walking, pressure, or cold ‘drawing’ sensation at the scar ‘tight’ sensation on walking * bases on 14 subjects. Indicated.
More than one complaint
could be
Table 3. Patients with severe complaints or symptoms loss of sensation neuropathic post-biopsy
Months since biopsy
diagnosis
W.K., (46 years), f
22
no definite diagnosis
J.O., (57 years), m
21
peroneal muscular atrophy
+++
M.-C., C., (38 years), f
12
peroneal muscular atrophy
+
+
pain on walking
L.G., (49 years), m
20
neuropathy of unknown aetiology
++
+++
electric shot-like sensations on pressure
H.E., (50 years), m
25
immunologic neuropathy
+++
+++
dysaesthesias on pressure, unable to wear other shoes than sandals
Patients
D (at the lower legs)
+++
?
complaints electric shoc-like sensations brought on by cold water and tight shoes pain brought on by cold and change of wheather
+ mild ++ medium +++ severe ? could not be assessed
Nine patients said, their discomfort was mild and very occasional. It did not interfere with their daily activities. One of these patients had had more severe complaints for 18 months after biopsy, but had improved by the time of examination. Five subjects (21%) complained of considerable discomfort since biopsy (Table 3). A 49-year-old woman was unable to wear tight shoes, especially boots, because of electricitylike-sensations. These dysaesthesias were also brought on by cold water, for instance when taking a shower. A 38-year-old woman complained of constant aching pain on walking. A 49-year-old woman was unable to wear tight vious to a change of weather. Two men with peripheral neuropathies reported that their sural nerve territories were sensitive even to mild touch. Circumscribed tenderness suggesting formation of neuromas was found in two patients. The tenderness could be alleviated by s.c.injection of a small amount of local anaesthetic (2 ml lidocaine 1%). No patient developed sympathetic dystrophy, which should always be considered as a cause of pain after a peripheral nerve lesion. Three of the five patients with more severe discomfort had extensive sensory loss in the
biopsied area, and two had considerable impairment of sensory functions due to their neuropathy. Patients with anaesthetic lower legs did not exhibit any symptoms. These findings suggest, that sensory impairment in the biopsied area does only prevent dysaesthias, if there is complete anaesthesia. In accordance with these results statistic tests (U-Test Mann-Whitney) revealed no significant correlation between the incidence of post-biopsy symptoms and the extension of biopsy related or generalized hypalgesia. Though several patients reported that their symptoms had improved during the first weeks or months after biopsy, we were unable to find a positive correlation between the interval since biopsy and the incidence or degree of discomfort. This does not necessarily mean that such a correlation does not exist, since patients with persisting symptoms may have been more likely to come to the follow-up examination. In the 5 patients with considerable symptoms biopsy was on average done 20 months earlier (range: 12 to 25 months). Discussion A nerve biopsy may be indicated in patients with peripheral neuropathy. The additional in195
Fig. 1. Maximum sensory defect after nerve biopsy
formation provided by the histological examination of a peripheral nerve must weigh up the eventual sequelae of the procedure. DYCK and LOFGREN' recommend six criteria a nerve chosen for biopsy should comply with: It should be (1) affected by the neuropathy (2) constant in its location (3) either pure sensory or pure motor (4) long enough so that to 10 cm of the same fascicles can be removed (5) located where entrapment or pressure are not common (6) suitable for conduction velocity studies in vitro. DYCK and LOFGREEN considered the sural nerve at ankle level most suitable in view of these criteria. It is located superficial to the deep muscle fascia and adjacent to the lesser saphenous vein. After an incision of 5 to 10 cm into the skin it can easily be removed. Some authors prefer fascicular biopsy, which is said to keep the sensory defects smalP2. The anatomic area supplied by the sural nerve is the lateral aspect of the foot. It comprises the area where branches of the sural nerve are found. The territory, which is exclusively innervated by the sural nerve, is referred to as area of autonomous supply. Its extension determines the final loss of sensation following transsection of the nerve. It varies considerably in size, depending on how far branches of neighbour sensory nerves extend to the sural nerve area and on the number of anastomoses between distal branches of different nerves (Fig. 1). The sural nerve generally has an autonomous region. Its average exten194
Fig. 2. Autonomous sensory areas at the lower leg (RI MU urltl
FOFKSI~
~1:)
sion as indicated by FOEKXER’” is shown in Fig. 2. FOERSTER already pointed out that in some cases a sensory defect may not occur in spite of complete transsection of the corresponding peripheral nerve. This is also true for the sural nerve. One of our patients exhibited no sensory impairment after biopsy. Nevertheless loss of sensation at the iateral aspect of the foot is the most constant aftereffect of sural nerve biopsy and could be demonstrated in all other patients of our study. POLLOCK et al.14 found sensory defects at a rate of 100% (16 patients) five or more years after biopsy. They showed that the extension of sensory loss was not significantiy smaller after fascicular biopsy compared to whole-nerve-biopsy. In addition to sensory impairment, some individuals experience pain or dysaesthesias of different degrees. These discomforts may persist for several months or even years. DY~K et al. I2 interviewed 134 patients one year after biopsy by a mailed questionnaire,
which was returned by 97 subjects. 60% indicated, they were free of any symptoms, 30 percent had mild discomfort, and 10% had considerable pain or dysaesthesias. In contrary to the findings of POLLOCK et a1.14, all patients evaluated five years after biopsy were free of symptoms. POLLOCK et af.14 reported tactile-induced dyaesthesias in 50% of their patients five years after biopsy. In our study loss of sensation was found in 17 out of a total of 18 evaluable subjects*. The extension had a mean of 45.7 cm2 (range 10.8 to 99.6), corresponding to 0.27% of body surface (range 0.06 to 0.35). The wide range of extension of hypalgesia corresponds to the variation of the autonomous area of the sural nerve, which cannot be anticipated. Many patients said that the area of sensory loss had become smaller during the first year after biopsy. Probably because of the considerable interindividual variation, however, there was no significant correlation between the time since biopsy and extension of hypalgesia. 14 out of 24 subjects (58%) reported persisting pain or dysaesthesias, which were considered as severe by 5 patients. In 9 subjects the discomfort did not prevent them from any everyday activities. The 5 patients (21%) with more severe symptoms seemed to be well adjusted. They carefully avoided inducing stimuli such as exposure to cold or pressure. No causalgia-like symptoms were found in any patient of this study. Evidence of neuroma could be demonstrated in two patients. The incidence of both mild and severe discomfort is considerable higher than indicated by DYCK et al.’ The studies, however, are not comparable. Our patients had to present them for a follow-up examination, whereas the patients of DYCK et al. filled in a questionnaire at home, which was to be sent back by mail. It can be assumed that symptom-free patients are not as likely to come for an examination than those with symptoms, but may consuent to filling in a form. Therefore, the incidence of severe symptoms would probably have been much smaller in our study, if it had been possible to examine all patients, who had undergone nerve biopsy. Frequency and severity of symptoms are not sifnificantly
related to the degree of neuropathic or postbiopsy hypalgesia. Even patients with marked sensory loss at the lower legs reported persisting symptoms after biopsy. Patients with complete anaesthesia exhibited no symptoms. The number of patients examined was too small for an accurate determination of the relation between complaints and the preexisting disease, which was the indication for biopsy. Conclusions Nerve biopsy might be considered as a valuable help for establishing the diagnosis. However, patients should be warned that this procedure may give rise to annoying symptoms for several months up to years, even though the intensity of pain never reaches that of causalgia. The incidence of persisting and more severe symptoms probably does not exceed lo%, if the total of biopsied patients is taken into account. The majority of patients will have only mild sensory loss and occasional slight pain and dysaesthesias. Patients with pre-existing complete anaesthesia will not have any sensory sequelae. Nevertheless, we consider nerve biopsies as necessary, provided there is a specific question and the specimen can be examined properly. References APPENZELLER 0, SNYDER RD, KORNFELD
M. Sural nerve
biopsies in pediatric neurological disorders. Develop Med Child Neurol 1970; 12:42+X. NYLAND H, MARIRE R, hi bRKS. ImmUnOlOgiCatcharacterization of sural nerve biopsies from patients with Guillain-Barre syndrome. Ann Neurol 1981; 980-6. VOSAJS, IOOSl’ENEMG,GABREELS-FESTEN AAM,GABREELS NM, KRUGSMAN JB, RENIERwo. 8uraf nerve biopsy in the diagnosis of progressive cerebral degenerative disorders of childhood. A retrospective study. Clin Neural Neurosurg 1982; 84:237-45. SCHLOTEw. Bioptische Untersuchungen am Nervensystem. Munch Med Wschr 1977; 119:927-32. BEHSEF. Nerve biopsy and conduction velocity along the sural nerve in diabetic neuropathy. Hormone and Metabolic Research, Suppl. Series 9 (Aspects of autonomic neuropathy in diabetes), 1980, 29. STARKE, B~HM M. Polyneuropathie vom LandryVerlaufstyp bei allergischer Granulomatose und Angiitis (Churg-Strauss-Syndrom). Akt Neural 1984; 11:44-6. DYCK PJ, LOFGREN EP. Nerve biopsy - Choice of nerve, method, symptoms, and usefulness. Medical Clinics of North America 1968; 52:885-78.
* One patient was unable to cooperate in the examination of sensory functions, five had too severe neuropathic hypaesthesia.
197
IO
Ii
ASBURY AK, CONOLLY ES. Sural nerve biopsy. Technical note. J Neurosurg 1973; 28:391-2. ASBURY AK, JOHNSON K, JOHNSON PC. Pathology of the peripheral nerve. In: Major problems of pathology. Philadelphia: Saunders WB 1978; 9:268-71. MUMENTHALER M, SCHLIACK H. LtiSiOnen peripherer Nerven. Stuttgart: Georg Thieme Verlag 1982. OMER GE, SPINNER M. Management of peripheral nerve problems. London: Saunders WB 1980.
198
DYCK PI. KARNES J. LAIS A. I.OFGREN EP. sit-VttiSI(.
Pathologic alterations of the peripheral nervous system of human. In: Dyck PJ. Thomas PK, Lambert EH. Bunge R eds. Peripheral Neuropathy. Philadelphia: Saunders WB. 2nd ed. 1984. auMKt:o, FOERS~EH o. Handbuch der Neurolo~le. Suppl. - Bd. II, Berlin: Springer 1928. POLLOCK M, NUKADA 0. Comparison
H,TAvLORP, DONALDSON
~.~ARROLI.
between fascicular and whole sural nerve biopsy. Ann Neural 1983; 13:65-S.
Introduction
Summary
Nerve biopsies are usually carried out as a diagnostic routine procedure in polyneuropathies and degenerative conditions of the nervous system1-5. The histological examination provides information on involvement of the peripheral neuron in the pathologic process. But only in a few conditions a specific diagnosis can be made on the basis of the histological findings (e.g. STARK und B6HM6). Generally dteI?itiOnS Of peripheral nerves such as demyelination or axonal degeneration may have a variety of aetiologies. In so far the value of this method for clinical purposes is limited, whereas for research it still is extremely helpfu12. Different nerves had been chosen for biopsy in the past. According to the recommendations of DYCK and LOFGREN' most authors have come to prefer the sural nerve at ankle level. It has no motor fibres so that biopsy cannot give rise to a motor deficit. Because of its superficial location above the deep muscle fascia and adjacent to the lesser saphenous vein the nerve is easily accessible*. At the ankle region the whole nerve can be removed over a length of 3 to 8 cm. In order to minimize subsequent loss of sensation some authors remove only a few fascicles by microsurgery and preserve the continuity of the nerve trunk. Biopsies of peripheral nerves are often referred to as minor operations with no conse*Neurologische
Klinik der Medirinischen
Sequelae of sural nerve biopsy were examined in 24 patients. Fourteen subjects reported persisting pain or dysaesthesias for more than one year. In nine patients the symptoms were mild, in five severe. Hypaesthesia of the lateral aspect of the foot was found in 17 out of 18 patients with otherwise normal or only slightly impaired sensory function. In one patient sural nerve biopsy did not cause permanent sensory loss. Pain and dysaesthesia were not significantly related to post-biopsy or generalized hypaesthesia. Key words: Sural nerve biopsy, follow-up examination, sequelae
quences other than mild sensory 10s~‘~~.On the other hand it is well known that even minor injuries of distal branches of the median nerve can cause painful burning sensations resembling causalgialOJ1. These sensations are triggered by pressure or cold. Furthermore patients may complain of dysaesthesias in the sensory area of the damaged nerve induced again by tactile or thermic stimuli. The proximal parts of completely seperated nerves may transform into neuromas, which tend to be extremely tender to touch or pressure. As the sural nerve biopsy is a merely diagnostic procedure, it is important to know, whether or not it may give rise to troublesome symptoms
Hochschule Hannover (Direktor: Prof. Dr. H. Schliack)
Address for correspondence and reprint requests: J.-P. Malin, Neurologische Konstanty-Gutschow-Strasse 8, 3ooO Hannover 61, FRG. Accepted
Klinik der Medizinischen Hochschule Hannover,
11.6.85
Clin Neurol Neurosurg 1985. Vol. 87-3.
193
other than loss of sensation. We report a followup study of 24 patients, who had undergone sural nerve biopsy more than one year earlier.
Table
1. Diagnosis
of biopsied
patients
;-----c;
Patients and method. In a four years period (1979-1983) 82 biopsies in neurologic patients had been carried out for diagnosis of peripheral neuropathies and metabolic or degenerative diseases of the nervous system. The biopsy had been taken at ankle level under local anaesthesia. lo-20 ml lidocaine 1% was injected subcutaneously from just behind the distal malleolus to about 8 cm proximally. The incision was made along the course of the lesser saphenous vein over a length of 5 to 8 cm. After retraction of the vein the sural nerve could be removed. It was divided first proximally with a scalpel to render the distal cut painless. The nerve stumps needed no further treatment. The biopsy specimen was immediately immerged in fixation fluid. After hemostasis the skin was reapproximated and a dry dressing was applied. Usually the patients were immobilized for 24 hours. All patients received an invitation to come to a follow-up examination, to which 24 (29%) appeared. They were aged 20 to 71 years (mean 47, median 43.4), and biopsy was done 1 to 4 years before (mean to 2.1, median 2 years). All patients had a full neurological examination. The extension of sensory deficit in the sural nerve territory was assessed by pinprick, marked on the foot, and copied on transparent plastic sheets. The area was measured by a computerized digitizer (ZEISS IBAS I). Sensory loss relative to body surface was computed. Sensitivity for light touch, temperature and vibration were not evaluated, as most patients were not able to localize deficits of these modalities exactly on repeated trials, whereas the extension of hypalgesia could be determined with sufficient reliability. The biopsy incision site and the denervated area were palpated for hyperalgesia and evidence of neuroma. Primary disease: 18 patients (75%) suffered from polyneuropathies which in 3 cases were caused by diabetes mellitus and in 4 cases by immunological diseases. 7 subjects had neuronal atrophies. In 4 cases the aetiology was unknown. 9 patients had 194
considerable hypaesthesia in both lower legs due to the neuropathies. In 8 patients biopsies were done for evaluation of other systemic disorders of the nervous system, which did not exclusively affect the peripheral neuron (Table 1). One subject was finally diagnosed to have a myopathy. Results Loss of sensation
Although the sural nerve had been completely separated in all individuals, sensory deficits had a wide intra-individual range. It has a mean extension of 45,7 cm* (range 10.8 to 99.6) corresponding to 0.27% of the body surface (range .06 to .37). In some cases hypalgesia was confined to a circular area with a diameter of about 3 cm distal the lateral malleolus. One woman with normal function of peripheral neurons had no loss of sensation at all. In 5 patients with severe neuropathic hypaesthesia in both lower legs no additional sensory impairment resulting from biopsy could be determined. One deafmute patient was unable to cooperate, when sensory functions were examined. Most patients reported that the area of numbness had been larger immediately after biopsy. Discomfort 14 out of 24 patients
(58%) had more or less severe discomfort in the sural nerve territory. They reported different kinds of paraesthesias or aching pain (Table 2). Three subjects considered the hypalgesia itself as troublesome. Table
2. Complaints
at follow-up*
electric shoe-like sensation ‘prickling’ on touch or pressure burning pain, brought on by walking, pressure, or cold ‘drawing’ sensation at the scar ‘tight’ sensation on walking * bases on 14 subjects. Indicated.
More than one complaint
could be
Table 3. Patients with severe complaints or symptoms loss of sensation neuropathic post-biopsy
Months since biopsy
diagnosis
W.K., (46 years), f
22
no definite diagnosis
J.O., (57 years), m
21
peroneal muscular atrophy
+++
M.-C., C., (38 years), f
12
peroneal muscular atrophy
+
+
pain on walking
L.G., (49 years), m
20
neuropathy of unknown aetiology
++
+++
electric shot-like sensations on pressure
H.E., (50 years), m
25
immunologic neuropathy
+++
+++
dysaesthesias on pressure, unable to wear other shoes than sandals
Patients
D (at the lower legs)
+++
?
complaints electric shoc-like sensations brought on by cold water and tight shoes pain brought on by cold and change of wheather
+ mild ++ medium +++ severe ? could not be assessed
Nine patients said, their discomfort was mild and very occasional. It did not interfere with their daily activities. One of these patients had had more severe complaints for 18 months after biopsy, but had improved by the time of examination. Five subjects (21%) complained of considerable discomfort since biopsy (Table 3). A 49-year-old woman was unable to wear tight shoes, especially boots, because of electricitylike-sensations. These dysaesthesias were also brought on by cold water, for instance when taking a shower. A 38-year-old woman complained of constant aching pain on walking. A 49-year-old woman was unable to wear tight vious to a change of weather. Two men with peripheral neuropathies reported that their sural nerve territories were sensitive even to mild touch. Circumscribed tenderness suggesting formation of neuromas was found in two patients. The tenderness could be alleviated by s.c.injection of a small amount of local anaesthetic (2 ml lidocaine 1%). No patient developed sympathetic dystrophy, which should always be considered as a cause of pain after a peripheral nerve lesion. Three of the five patients with more severe discomfort had extensive sensory loss in the
biopsied area, and two had considerable impairment of sensory functions due to their neuropathy. Patients with anaesthetic lower legs did not exhibit any symptoms. These findings suggest, that sensory impairment in the biopsied area does only prevent dysaesthias, if there is complete anaesthesia. In accordance with these results statistic tests (U-Test Mann-Whitney) revealed no significant correlation between the incidence of post-biopsy symptoms and the extension of biopsy related or generalized hypalgesia. Though several patients reported that their symptoms had improved during the first weeks or months after biopsy, we were unable to find a positive correlation between the interval since biopsy and the incidence or degree of discomfort. This does not necessarily mean that such a correlation does not exist, since patients with persisting symptoms may have been more likely to come to the follow-up examination. In the 5 patients with considerable symptoms biopsy was on average done 20 months earlier (range: 12 to 25 months). Discussion A nerve biopsy may be indicated in patients with peripheral neuropathy. The additional in195
Fig. 1. Maximum sensory defect after nerve biopsy
formation provided by the histological examination of a peripheral nerve must weigh up the eventual sequelae of the procedure. DYCK and LOFGREN' recommend six criteria a nerve chosen for biopsy should comply with: It should be (1) affected by the neuropathy (2) constant in its location (3) either pure sensory or pure motor (4) long enough so that to 10 cm of the same fascicles can be removed (5) located where entrapment or pressure are not common (6) suitable for conduction velocity studies in vitro. DYCK and LOFGREEN considered the sural nerve at ankle level most suitable in view of these criteria. It is located superficial to the deep muscle fascia and adjacent to the lesser saphenous vein. After an incision of 5 to 10 cm into the skin it can easily be removed. Some authors prefer fascicular biopsy, which is said to keep the sensory defects smalP2. The anatomic area supplied by the sural nerve is the lateral aspect of the foot. It comprises the area where branches of the sural nerve are found. The territory, which is exclusively innervated by the sural nerve, is referred to as area of autonomous supply. Its extension determines the final loss of sensation following transsection of the nerve. It varies considerably in size, depending on how far branches of neighbour sensory nerves extend to the sural nerve area and on the number of anastomoses between distal branches of different nerves (Fig. 1). The sural nerve generally has an autonomous region. Its average exten194
Fig. 2. Autonomous sensory areas at the lower leg (RI MU urltl
FOFKSI~
~1:)
sion as indicated by FOEKXER’” is shown in Fig. 2. FOERSTER already pointed out that in some cases a sensory defect may not occur in spite of complete transsection of the corresponding peripheral nerve. This is also true for the sural nerve. One of our patients exhibited no sensory impairment after biopsy. Nevertheless loss of sensation at the iateral aspect of the foot is the most constant aftereffect of sural nerve biopsy and could be demonstrated in all other patients of our study. POLLOCK et al.14 found sensory defects at a rate of 100% (16 patients) five or more years after biopsy. They showed that the extension of sensory loss was not significantiy smaller after fascicular biopsy compared to whole-nerve-biopsy. In addition to sensory impairment, some individuals experience pain or dysaesthesias of different degrees. These discomforts may persist for several months or even years. DY~K et al. I2 interviewed 134 patients one year after biopsy by a mailed questionnaire,
which was returned by 97 subjects. 60% indicated, they were free of any symptoms, 30 percent had mild discomfort, and 10% had considerable pain or dysaesthesias. In contrary to the findings of POLLOCK et a1.14, all patients evaluated five years after biopsy were free of symptoms. POLLOCK et af.14 reported tactile-induced dyaesthesias in 50% of their patients five years after biopsy. In our study loss of sensation was found in 17 out of a total of 18 evaluable subjects*. The extension had a mean of 45.7 cm2 (range 10.8 to 99.6), corresponding to 0.27% of body surface (range 0.06 to 0.35). The wide range of extension of hypalgesia corresponds to the variation of the autonomous area of the sural nerve, which cannot be anticipated. Many patients said that the area of sensory loss had become smaller during the first year after biopsy. Probably because of the considerable interindividual variation, however, there was no significant correlation between the time since biopsy and extension of hypalgesia. 14 out of 24 subjects (58%) reported persisting pain or dysaesthesias, which were considered as severe by 5 patients. In 9 subjects the discomfort did not prevent them from any everyday activities. The 5 patients (21%) with more severe symptoms seemed to be well adjusted. They carefully avoided inducing stimuli such as exposure to cold or pressure. No causalgia-like symptoms were found in any patient of this study. Evidence of neuroma could be demonstrated in two patients. The incidence of both mild and severe discomfort is considerable higher than indicated by DYCK et al.’ The studies, however, are not comparable. Our patients had to present them for a follow-up examination, whereas the patients of DYCK et al. filled in a questionnaire at home, which was to be sent back by mail. It can be assumed that symptom-free patients are not as likely to come for an examination than those with symptoms, but may consuent to filling in a form. Therefore, the incidence of severe symptoms would probably have been much smaller in our study, if it had been possible to examine all patients, who had undergone nerve biopsy. Frequency and severity of symptoms are not sifnificantly
related to the degree of neuropathic or postbiopsy hypalgesia. Even patients with marked sensory loss at the lower legs reported persisting symptoms after biopsy. Patients with complete anaesthesia exhibited no symptoms. The number of patients examined was too small for an accurate determination of the relation between complaints and the preexisting disease, which was the indication for biopsy. Conclusions Nerve biopsy might be considered as a valuable help for establishing the diagnosis. However, patients should be warned that this procedure may give rise to annoying symptoms for several months up to years, even though the intensity of pain never reaches that of causalgia. The incidence of persisting and more severe symptoms probably does not exceed lo%, if the total of biopsied patients is taken into account. The majority of patients will have only mild sensory loss and occasional slight pain and dysaesthesias. Patients with pre-existing complete anaesthesia will not have any sensory sequelae. Nevertheless, we consider nerve biopsies as necessary, provided there is a specific question and the specimen can be examined properly. References APPENZELLER 0, SNYDER RD, KORNFELD
M. Sural nerve
biopsies in pediatric neurological disorders. Develop Med Child Neurol 1970; 12:42+X. NYLAND H, MARIRE R, hi bRKS. ImmUnOlOgiCatcharacterization of sural nerve biopsies from patients with Guillain-Barre syndrome. Ann Neurol 1981; 980-6. VOSAJS, IOOSl’ENEMG,GABREELS-FESTEN AAM,GABREELS NM, KRUGSMAN JB, RENIERwo. 8uraf nerve biopsy in the diagnosis of progressive cerebral degenerative disorders of childhood. A retrospective study. Clin Neural Neurosurg 1982; 84:237-45. SCHLOTEw. Bioptische Untersuchungen am Nervensystem. Munch Med Wschr 1977; 119:927-32. BEHSEF. Nerve biopsy and conduction velocity along the sural nerve in diabetic neuropathy. Hormone and Metabolic Research, Suppl. Series 9 (Aspects of autonomic neuropathy in diabetes), 1980, 29. STARKE, B~HM M. Polyneuropathie vom LandryVerlaufstyp bei allergischer Granulomatose und Angiitis (Churg-Strauss-Syndrom). Akt Neural 1984; 11:44-6. DYCK PJ, LOFGREN EP. Nerve biopsy - Choice of nerve, method, symptoms, and usefulness. Medical Clinics of North America 1968; 52:885-78.
* One patient was unable to cooperate in the examination of sensory functions, five had too severe neuropathic hypaesthesia.
197
IO
Ii
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