Progressive idiopathic axonal neuropathy

Abstract. Patients with a progressive disabling idiopathic axonal neuropathy could have a potentially treatable immune mediated neuropathy. To evaluate whether progressive idiopathic axonal neuropathy could be a pathologically difficult to prove vasculitic neuropathy pathologically difficult to prove or if it could be a separate clinical entity (i. e. with the axon as the primary immunological target), we performed a comparative clinical and histopathological study in 10 patients with progressive idiopathic axonal neuropathy, 10 patients with vasculitic neuropathy, and 12 patients with chronic idiopathic axonal polyneuropathy (CIAP). The clinical features and disease course in patients with progressive idiopathic axonal neuropathy and patients with vasculitic neuropathy were similar. Six patients with progressive idiopathic axonal neuropathy had been treated with prednisone and/or intravenous immunoglobulin. Disability decreased in all these six patients, but also in two of the four non-treated patients. Upon reviewing the sural nerve biopsy specimens, vasculitis was found in one patient with progressive idiopathic axonal neuropathy. Vasculitis-associated signs of ischemic injury or inflammation (most notably: large variation in fascicular axonal degeneration, perivascular inflammation, inflammation of the blood vessel wall without lumen obstruction) were found in four patients with progressive idiopathic axonal neuropathy, in all patients with vasculitic neuropathy, but were absent in patients with CIAP. The findings show that there is a small chance of finding sural nerve vasculitis upon scrutinising biopsy examination in progressive idiopathic axonal neuropathy. The presence of vasculitisassociated signs in progressive idiopathic axonal neuropathy suggests that some of these patients could have vasculitic neuropathy, even if vasculitic lesions cannot be demonstrated. However, if inflammatory changes cannot be demonstrated this does not preclude an immune-mediated origin.     

The additional yield of combined nerve/muscle biopsy in vasculitic neuropathy

Background: Vasculitic neuropathy can be confirmed by demonstrating vasculitis in a nerve biopsy, but it is uncertain to what extent combined (i.e. nerve/muscle) biopsy improves the yield. Methods: A random‐effects meta‐analysis was performed to assess the additional yield of combined biopsy in vasculitic neuropathy. Medline, Embase, LILACS and ISI were searched from January 1980 until January 2009 for relevant articles on the yield of nerve, muscle or combined biopsy to diagnose vasculitic neuropathy. Fourteen (15%) studies were included. Methodological quality was scored using a modified Quality Assessment for Diagnostic Accuracy Studies tool. Results: In patients clinically suspected of vasculitic neuropathy, the additional yield of definite vasculitis in combined biopsy was 5.1% (95% CI 1.1–9.2%; P = 0.013). In patients diagnosed with vasculitic neuropathy, the additional yield of definite vasculitis in combined biopsy was 15% (95% CI 2.1–28%; P = 0.023). Conclusions: There is a modest additional yield of definite vasculitis in combined biopsy compared to nerve biopsy alone. Because of methodological flaws in analysed studies, the findings should be validated in a prospective study.     

Skin denervation in vasculitic neuropathy

BACKGROUND: Skin denervation in vasculitic neuropathy has rarely been documented despite frequent manifestations of small-fiber neuropathy including reduced sensitivity and neuropathic pain. Recently, skin biopsy has been established as a new approach to diagnose small-fiber sensory neuropathy. OBJECTIVES: To investigate the pathologic features of cutaneous nerves and to evaluate inflammatory vasculopathy in the skin of patients with vasculitis. DESIGN: Case series. SETTING: National Taiwan University Hospital, Taipei.Patients Six patients with vasculitic neuropathy. INTERVENTIONS: Patients had 3-mm punch biopsy specimens taken from the distal part of the leg (without active vasculitic lesions) and a sural nerve biopsy specimen was taken in addition to detailed neurologic examinations, laboratory investigations, and nerve conduction studies. MAIN OUTCOME MEASURES: Results of nerve conduction studies, epidermal nerve fiber density studies, and immunohistochemistry. RESULTS: All 6 patients had combined large- and small-nerve-fiber involvement on the neurologic examinations. Nerve conduction studies showed a pattern of axonal neuropathy or mononeuropathy multiplex. Epidermal nerve fiber densities were significantly reduced in the skin of all patients, consistent with concomitant small-fiber neuropathies. Perivascular infiltration by T cells and macrophages was demonstrated by immunohistochemistry. All patients experienced neurologic improvement in muscle strength and alleviation of sensory symptoms after immunotherapy with corticosteroids, plasma exchange, or cyclophosphamide. CONCLUSIONS: Small-diameter sensory nerves are affected in vasculitis in addition to the well-known effect of vasculitis on large-diameter nerves. Significant inflammatory vasculopathy is present in the skin despite the absence of clinically active vasculitic lesions.     

Superficial peroneal nerve/peroneus brevis muscle biopsy in vasculitic neuropathy

OBJECTIVE: To determine the sensitivity and specificity of superficial peroneal nerve (SPN)/peroneus brevis muscle (PBM) biopsy in a cohort of patients with suspected peripheral nerve vasculitis. BACKGROUND: In patients with suspected vasculitic neuropathy, combined nerve and muscle biopsies have been advocated as a way to increase the diagnostic yield, but the sensitivity and specificity of this approach have not been evaluated. Pathologic predictors of biopsy-proven peripheral nerve vasculitis have also not been analyzed in a systematic fashion. METHODS: The clinical, laboratory, and pathologic data for all patients undergoing SPN/PBM biopsy for possible vasculitis from 1986 through 1996 were analyzed. Biopsies were classified as positive, negative, or suspicious for vasculitis. Patients were then divided into vasculitis and nonvasculitis cohorts by final clinical diagnosis. RESULTS: Of 70 SPN/PBM biopsies, 22 (30%) showed definite vasculitis; nerve was diagnostic in 90% (n = 20) and muscle in 50% (n = 11). Nerve biopsy had a higher yield than muscle in patients with nonsystemic vasculitic neuropathy (p = 0. 0047) but not in those with systemic vasculitis. The estimated sensitivity of a positive SPN/PBM biopsy for vasculitis was 60%. Considering biopsies either positive or suspicious for vasculitis increased the sensitivity to 86% with a corresponding specificity of 85%. Pathologic features associated with necrotizing vasculitis were muscle fiber necrosis/regeneration (relative risk 18.1; 95% CI 3.4 to 96.1), predominant axonal nerve pathology (>8.8; >1.0 to 77.4), Wallerian-like degeneration (5.6; 1.4 to 21.9), and asymmetric nerve fiber loss (4.6; 1.4 to 15.9). CONCLUSIONS: These findings establish the yield, sensitivity, and specificity of SPN/PBM biopsy for diagnosing vasculitic neuropathy and validate the use of suggestive pathologic features for diagnosing cases lacking definite necrotizing vascular changes.     

Direct immunofluoresence in vasculitic neuropathy: Specificity of vascular immune deposits

In suspected vasculitic neuropathy, vasculitis is demonstrated in only 30% of superficial peroneal nerve (SPN)/peroneus brevis muscle (PBM) specimens. Pathologic predictors of vasculitis are thus needed for non‐diagnostic cases. Immune deposits in epineurial vessels have an established sensitivity but unknown specificity. In this study we assessed specificity using direct immunofluorescence (DIF) in SPN/PBM biopsies for suspected vasculitic neuropathy. Biopsies from 13 patients with vasculitis, 13 without vasculitis, and 6 with diabetic radiculoplexus neuropathy (DRPN) were stained for immunoglobulin G (IgG), IgM, and complement 3 (C3), and analyzed in a blinded manner. Vascular immunoglobulin or C3 deposits occurred in 12 of 13 nerve or muscle biopsies (11 of 13 nerves, 5 of 13 muscles) in vasculitis vs. 1 of 13 (1 of 13 nerves, 0 of 13 muscles) in controls (P = 0.00003). Specificity was 92%. For DRPN, vascular immune deposits occurred in 5 of 6 nerves or muscles (4 of 6 nerves, 1 of 5 muscles), similar to vasculitis but significantly different from controls. Epineurial/perimysial vascular deposits of immunoglobulin/C3 by DIF are a specific marker of vasculitic neuropathy. Muscle Nerve 000:000–000, 2009     

Sural mononeuropathy: A report of 36 cases

Introduction: Isolated sural mononeuropathy is rare and frequently constitutes a diagnostic challenge. Methods: This investigation was a retrospective study of sural neuropathy at a single electrodiagnostic center. Results: Our study included 36 patients with sural neuropathy, the largest sample so far reported. Non‐surgical, non‐traumatic etiologies account for 50% of the cases, including 7 patients with inflammatory or vasculitic conditions. Routine sural conduction study was positive in 34 of 36 patients, whereas a distal recording method was used to verify the diagnosis of sural mononeuropathy in 2 patients. Most (58%) patients did not require specific treatment, but persistent sensory symptoms were seen in a minority of cases. Sural nerve biopsy in 1 patient helped diagnostic and treatment planning. Conclusions: Sural mononeuropathy has distinct etiologic, clinical, and electrophysiological features. Recognition can be beneficial in treating patients with sensory symptoms involving the distal lower extremity. Muscle Nerve 49 :443–445, 2014     

Peripheral neuropathy in CADASIL

Background Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is a hereditary cerebral microangiopathy associated with mutations in the Notch 3 gene. The clinical phenotype is characterized by cerebral impairment even though typical microvascular changes are diffuse. Objective To assess peripheral neuropathy in patients with CADASIL. Patients and Methods We enrolled eleven CADASIL patients with variable phenotype including clinical signs of peripheral nerve involvement. In all patients electromyography and nerve conduction velocities were performed. Peripheral nerve biopsy was performed in three cases. Results We found sensory motor neuropathy in 7/11 patients. Nerve biopsy revealed axonal and demyelinated findings. Conclusion Our findings suggest that peripheral neuropathy may be part of the CADASIL phenotype.     

Vasculitic peripheral neuropathy in deficiency of adenosine deaminase 2

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive inflammatory vasculopathy characterized by systemic vasculitis, early-onset stroke and livedo racemosa. We report a family cohort of 3 patients with ADA2 compound heterozygous mutation p.[Thr360Ala] and [Gly383Ser]. Two of them had progressive involvement of the peripheral nervous system in the fourth decade, both after stroke. In one patient, clinical and neurophysiological studies showed progression of mononeuritis multiplex to chronic axonal sensorimotor polyneuropathy, nerve biopsy had features of small vessel vasculitic neuropathy, and muscle biopsy disclosed neurogenic atrophy with reinnervation. The second patient presented with progressive sensory symptoms of the lower limbs and chronic axonal sensorimotor polyneuropathy in nerve conduction studies. These two patients had absent plasma ADA2 activity. The third patient had no neurological affection despite low, but not absent, plasma ADA2 activity. Patients were started on a tumor necrosis factor (TNF) inhibitor, which has presumed benefits for the vasculitic phenotype of DADA2.     

Vasculitic neuropathy: Comparison of clinical predictors with histopathological outcome

Introduction:To improve diagnostic accuracy, in this study we compared prebiopsy clinical parameters with subsequent pathological confirmation of peripheral nerve vasculitis. Methods: Clinical, laboratory, and neurophysiological parameters were analyzed for consecutive patients referred for nerve biopsy with suspected vasculitis. Patients were assigned pathological categories of definite, probable, possible, or absent vasculitis using validated guidelines. Patients with definite or probable vasculitis were considered to have pathologically confirmed vasculitis. Results: From a cohort of 78 patients, biopsy confirmed vasculitis in 29.5%. Parameters that best differentiated between pathologically confirmed and pathologically unlikely vasculitis were stepwise clinical progression (34.8% vs. 5.6%), the presence of serum anti-myeloperoxidase antibody (28.6% vs. 2.2%) and rheumatoid factor seropositivity (38.1% vs. 10.7%). Pathologically absent vasculitis was frequent in patients with normal (100%) or primarily demyelinating (87.5%) nerve conduction studies. Discussion: Factoring the negative predictors of pathologically confirmed vasculitis into decision-making can reduce the frequency of diagnostically unhelpful nerve biopsies. Muscle Nerve 59:643–649, 2019     

Conduction block in vasculitic neuropathy

Vasculitis involving peripheral nerves usually presents as an acute asymmetrical axonal neuropathy. We report a 67-year-old man with a symmetrical subacute neuropathy in which nerve conduction studies showed prominent conduction block, a finding indicative of demyelination. Sural nerve biopsy showed a vasculitic neuropathy with invasion of blood vessel walls by inflammatory cells and a mixture of nerve fiber loss and demyelination. The demyelination in this case was presumably a consequence of subinfarctive nerve ischemia. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:1084–1088, 1998.     

Neurological manifestations of chronic hepatitis C

Hepatitis C virus (HCV) infection is often associated with abnormal immunological responses. We describe four patients with vasculitic neurological signs and symptoms following HCV infection. A 56-year-old woman with HCV infection developed peripheral neuropathy characterized by asymmetric distal painful hypesthesia, dysesthesia and moderate motor weakness of the lower limbs. Serological examinations revealed cryoglobulinemia and low levels of complement C4. A biopsy of the sural nerve revealed vasculitic neuropathy. HCV infection associated immunomediated vasculitis was diagnosed. While steroid therapy was ineffective, treatment with interferon-α improved the neuropathy considerably without, however, eliminating HCV infection. A 62-year-old man with HCV infection developed peripheral sensory neuropathy. Complement C3 was slightly diminished. Nerve biopsy revealed vasculitic neuropathy. A 71-year-old woman developed chronic symmetric sensomotor polyneuropathy. HCV hepatitis followed blood transfusions. Cryoglobulins tested positive, consistent with type II cryoglobulinemia. Complements C3 and C4 were diminished. Inflammatory infiltrates in the sural nerve biopsy specimen led to the diagnosis of chronic vasculitic disorder. A 55-year-old woman with HCV infection developed vasculitis of the skin, connective tissue, visceral organs, and kidney, leading to hemodialysis. Neurologically she developed severe apathy and drowsiness, myoclonic jerks, exaggerated deep tendon reflexes, and positive pyramidal signs. Magnetic resonance imaging of the brain showed diffuse increased signal abnormalities involving supra- and infratentorial white matter suggesting cerebral vasculitis. Cryoglobulins were positive, complements C3 and C4 slightly diminished (54 mg/dl, 4.3 mg/dl). Supportive therapy resulted in neurological improvement. Treatment with interferon-α was discontinued because of agranulocytosis. In patients with peripheral neuropathy or signs of leucencephalopathy, a hepatitis C associated vasculitis should be considered in the differential diagnosis. Received: 13 July 1998 Received in revised form: 24 September 1998 Accepted: 10 November 1998     

Usefulness of superficial peroneal nerve/peroneus brevis muscle biopsy in the diagnosis of vasculitic neuropathy

Sensitivity, specificity, and diagnostic yield of the superficial peroneal nerve (SPN)/peroneus brevis muscle (PBM) biopsy in 43 patients with clinically suspected vasculitic neuropathy was studied. Biopsies were classified as “definite”, “suspicious” or “possible” in accordance with established criteria. Vasculitis was detected in 27 patients (21 with non-systemic vasculitis, and six with systemic vasculitis). In patients with “definite” vasculitis (n = 13), the sensitivity of SPN/PBM biopsy was 76.4% with 100% specificity. By including patients suspicious for vasculitis (n = 10), sensitivity increased to 85.1% but the specificity dropped to 87.5%. The overall diagnostic yield of SPN biopsy in those patients with definite vasculitis was 76.9% (10/13), and 53.8% (7/13) for muscle biopsy. The addition of muscle biopsy increased the diagnostic yield by 23%. Asymmetric nerve fiber loss, Wallerian degeneration and presence of hemosiderin were statistically significant markers of probable vasculitis. Muscle tissue was more likely to show hemosiderin (85.7%) than a nerve biopsy (71%). A combined SPN/PBM biopsy offers excellent diagnostic yield in the diagnosis of vasculitic neuropathy.     

Peripheral Nerve Society Guideline on the classification, diagnosis, investigation, and immunosuppressive therapy of non-systemic vasculitic neuropathy: executive summary

Non-systemic vasculitic neuropathy (NSVN) is routinely considered in the differential diagnosis of progressive axonal neuropathies, especially those with asymmetric or multifocal features. Diagnostic criteria for vasculitic neuropathy, classification criteria for NSVN, and therapeutic approaches to NSVN are not standardized. The aim of this guideline was to derive recommendations on the classification, diagnosis, investigation, and treatment of NSVN based on the available evidence and, where evidence was not available, expert consensus. Experts on vasculitis, vasculitic neuropathy, and methodology systematically reviewed the literature for articles addressing diagnostic issues concerning vasculitic neuropathy and NSVN as well as treatment of NSVN and the small-to-medium vessel primary systemic vasculitides using MEDLINE, EMBASE, and the Cochrane Library. The selected articles were analyzed and classified. The group initially reached consensus on a classification of vasculitides associated with neuropathy. Non-diabetic radiculoplexus neuropathy was incorporated within NSVN. The consensus definition of pathologically definite vasculitic neuropathy required that vessel wall inflammation be accompanied by vascular damage. Diagnostic criteria for pathologically probable vasculitic neuropathy included five predictors of definite vasculitic neuropathy: vascular deposits of IgM, C3, or fibrinogen by direct immunofluorescence; hemosiderin deposits; asymmetric nerve fiber loss; prominent active axonal degeneration; and myofiber necrosis, regeneration, or infarcts in peroneus brevis muscle biopsy (Good Practice Points from class II/III evidence). A case definition of clinically probable vasculitic neuropathy in patients lacking biopsy proof incorporated clinical features typical of vasculitic neuropathy: sensory or sensory-motor involvement, asymmetric/multifocal pattern, lower-limb predominance, distal-predominance, pain, acute relapsing course, and non-demyelinating electrodiagnostic features (Good Practice Points from class II/III evidence). Proposed exclusionary criteria for NSVN--favoring the alternate diagnosis of systemic vasculitic neuropathy--were clinicopathologic evidence of other-organ involvement; anti-neutrophil cytoplasmic antibody (ANCAs); cryoglobulins; sedimentation rate ≥100 mm/h; and medical condition/drug predisposing to systemic vasculitis (Good Practice Points supported by class III evidence). Three class III studies on treatment of NSVN were identified, which were insufficient to permit a level C recommendation. Therefore, the group reviewed the literature on treatment of primary small-to-medium vessel systemic vasculitides prior to deriving Good Practice Points on treatment of NSVN. Principal treatment recommendations were: (1) corticosteroid (CS) monotherapy for at least 6 months is considered first-line; (2) combination therapy should be used for rapidly progressive NSVN and patients who progress on CS monotherapy; (3) immunosuppressive options include cyclophosphamide, azathioprine, and methotrexate; (4) cyclophosphamide is indicated for severe neuropathies, generally administered in IV pulses to reduce cumulative dose and side effects; (5) in patients achieving clinical remission with combination therapy, maintenance therapy should be continued for 18-24 months with azathioprine or methotrexate; and (6) clinical trials to address all aspects of treatment are needed.     

Cutaneous activation of rage in nonsystemic vasculitic and diabetic neuropathy

Introduction: We asked whether the receptor of advanced glycation end products (RAGE) is related to dermal inflammation in nonsystemic vasculitic neuropathy (NSVN) and diabetic neuropathy (DN) and whether its presence in skin is comparable to that in sural nerve biopsies. Methods: We immunoreacted skin biopsy samples from 17 NSVN and 7 DN patients who had also undergone sural nerve biopsy, and 14 healthy controls with antibodies to advanced glycation end products (AGE), RAGE, T‐cells, and macrophages. Results: AGE and RAGE immunoreactivity were present in vessels of nerve biopsies from NSVN and DN. AGE and RAGE were increased in dermal endothelial cells and T‐cells of NSVN and DN patients compared with controls. Conclusions: Dermal RAGE is increased in NSVN and DN, supporting the concept of a role of the RAGE pathway in the pathophysiology of dermal inflammation and skin denervation in NSVN and DN. Muscle Nerve 50 : 377–383, 2014     

Spinal charcot‐marie‐tooth disease: A reappraisal

Introduction: Distal hereditary motor neuropathy (dHMN) is characterized by isolated distal muscle atrophy without sensory deficit. Nevertheless, clinical sensory loss has been reported despite preserved sensory nerve conduction in a few patients, thus differentiating these cases from the classical type 2 Charcot‐Marie‐Tooth disease (CMT2). Methods: We report 4 patients who presented with clinical sensory and motor neuropathy and normal peripheral sensory nerve conduction studies and were investigated with complete electrophysiological studies, including somatosensory evoked potentials (SEP). Results: These patients had a clinical presentation of classical CMT with isolated axonal motor neuropathy suggestive of dHMN. Interestingly, tibial nerve SEPs showed abnormalities suggestive of proximal involvement of dorsal roots that may explain the clinical somatosensory disturbances. Conclusions: These cases support the concept of spinal CMT that should be recognized as an intermediate form between dHMN and CMT2. SEP recording was helpful in defining a more precise phenotype of spinal CMT. Muscle Nerve 46: 603–607, 2012     

Management of non-motor complications in Parkinson’s disease

The problem of diagnosing vasculitic neuropathy is discussed based on case reports of two patients with Wegener’s granulomatosis. One patient developed de novo 6^th nerve palsy as an isolated relapse manifestation and the second patient a sequence of multiple cranial nerve palsies. Brain imaging with CT and MRI and the laboratory provided no clues suggesting active vasculitis. However, in both patients the neuropathies fully recovered in response to standard induction protocols of vasculitis. In the absence of organspecific proof of vasculitis, these treatment decisions were guided by the overall clinical presentations. Cranial neuropathy may be the first obvious vasculitic manifestation preceding other organ disease, and since single reliable tests for its diagnosis are lacking, a multidisciplinary approach is advocated here to detect vasculitic manifestations in other organs.     

Peripheral neuropathy in glycogen storage disease type III: Fact or myth?

Introduction: The aim of this study was to assess whether peripheral neuropathy is a feature of glycogen storage disease type IIIa (GSD IIIa) in adult patients. Methods: Medical records of a cohort of adult GSD IIIa patients who underwent electromyography (EMG) and nerve conduction studies (NCS) were reviewed, and the results were correlated with physical examination findings. Results: Sixteen patients underwent EMG and NCS; 4 complained of exercise intolerance, 1 of foot paresthesia, and 11 of muscle weakness (3 proximal, 8 distal). None of the patients had sensory deficits on clinical examination. All motor and sensory conduction velocities and sensory amplitudes were within reference ranges. EMG showed myopathic motor unit potentials in 15 of the 16 patients. Conclusions: Based on the clinical examination and the NCS and EMG results, we did not identify any peripheral nerve involvement in our adult patients diagnosed with GSD III. Muscle Nerve 53: 310–312, 2016     

Immunotherapy‐responsive allodynia due to distal acquired demyelinating symmetric (DADS) neuropathy

Introduction: Distal acquired demyelinating symmetric (DADS) neuropathy is a distal variant of chronic inflammatory demyelinating polyradiculoneuropathy. It is characterized by chronic distal symmetric sensory or sensorimotor deficits. Sensory ataxia is a common clinical presentation. Nerve conduction studies typically show markedly prolonged distal motor latencies. Methods: We report 2 patients with chronic progressive generalized pain and fatigue, with normal neurological examinations except for allodynia. Results: Nerve conduction studies were typical of DADS neuropathy. Monoclonal protein studies were negative. Cerebrospinal fluid protein levels were elevated. Sural nerve biopsies revealed segmental demyelination and remyelination. One biopsy had marked endoneurial and epineurial lymphocytic infiltration. Immunomodulatory therapy alleviated the pain and fatigue and markedly improved distal motor latencies in both patients. Conclusions: DADS neuropathy can present with pain and a normal neurological examination apart from allodynia. Nerve conduction studies are necessary for diagnosis. These patients respond to immunotherapy better than typical DADS neuropathy patients with sensory ataxia. Muscle Nerve 54 : 973–977, 2016     

Contribution of nerve biopsy to unclassified neuropathy

OBJECTIVES: To evaluate the diagnostic yield of nerve biopsy in patients with peripheral neuropathy of undetermined cause despite extensive diagnostic workup. METHODS: From November 2001 through January 2004, 38 patients underwent nerve biopsy because of unclassified neuropathy. RESULTS: The etiology of the neuropathies could be defined in 14 patients (37%), i.e. in 15% of chronic symmetric, 30% of chronic asymmetric, 50% of subacute symmetric and 62.5% of subacute asymmetric neuropathies. The biopsy was diagnostic in 6 patients (16%), where it showed a vasculitis, and supportive in 8 patients (21%). CONCLUSIONS: The contribution of nerve biopsy to the diagnosis of peripheral neuropathy was highest in acute and subacute asymmetric forms of neuropathy and lowest in chronic symmetric forms. The main indication for nerve biopsy remains the diagnosis of vasculitic neuropathy, a potentially treatable disorder.