Prospective study of the usefulness of sural nerve biopsy

The multiple roles of nerve biopsy in the diagnosis and prognosis of suspected immune neuropathies

INTRODUCTION

The value of a sural nerve biopsy for the diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is controversial. Evidence-based recommendations for its implementation are lacking. We investigated factors leading to biopsy and analyzed biopsy outcomes and consequences, assessed the predictability of biopsy outcomes through clinical parameters to avoid unnecessary biopsies, and compared results with electrophysiological and clinical severity to determine their prognostic value.

METHODS

190 sural nerve biopsies were analyzed in two cohorts. One consisted of 163 biopsies and the second of 72 biopsies from the prospective Immune-mediated Neuropathies Biomaterial and Data registry (INHIBIT). Both have an intersection of 45 patients. 75 data sets from patients without biopsy were used. Analysis of nerve conduction studies, treatment, overall disability sum score (ODSS), biopsy outcomes, and diagnosis was performed.

RESULTS

51% of biopsied patients received the diagnosis CIDP (77% fulfilled EFNS/PNS criteria), 21% were not CIDP typical, and 27% were unspecific. Biopsied patients responded less frequently to immunotherapies at time of biopsy than non-biopsied patients (p = 0.003). Immunotherapy was initiated more frequently after biopsy (p < 0.001) and more often with intravenous immunoglobulins (p < 0.0001). 76% of all biopsied patients met the electrophysiological criteria for CIDP. Sensory nerve action potential amplitudes of 0 µV still provide 73% of histological diagnostic value. Histologic signs of degeneration predicted ODSS worsening after 1 year (p = 0.028) but disease severity did not correlate with histological damage severity.

DISCUSSION

The main indication for nerve biopsy was the treatment of refractory cases of autoimmune neuropathies with the therapeutic consequence of treatment initiation or escalation. Sural biopsy also provided prognostic information. Even with extinguished sural SNAP, the biopsy can still have diagnostic value.

Relevance of Nerve Biopsy in the Diagnosis of Chronic Inflammatory Demyelinating Polyneuropathy—A Systematic Review

Chronic Inflammatory Demyelinating Polyneuropathy is an immune-mediated pathology of the peripheral nerves and nerve roots that leads to weakness and sensory symptoms. Given its clinical heterogeneity, often times diagnosis is challenging. Even though nerve conduction studies and clinical features are the main criteria used for diagnosis, supplementary investigations, such as nerve biopsies, cerebral spinal fluid examination and magnetic resonance studies, may be used in order to confirm the diagnosis. Given the fact that the hallmark in CIDP physiopathology is the demyelination process, nerve biopsies are used to demonstrate and assess the magnitude of the phenomenon. The question and the main interest of this review is whether histopathological findings are relevant for the diagnosis and can be useful in disease assessment.

Preclinical evidence for mitochondrial DNA as a potential blood biomarker for chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious dose-limiting side effect of several first-line chemotherapeutic agents including paclitaxel, oxaliplatin and bortezomib, for which no predictive marker is currently available. We have previously shown that mitochondrial dysfunction is associated with the development and maintenance of CIPN. The aim of this study was to evaluate the potential use of mitochondrial DNA (mtDNA) levels and complex I enzyme activity as blood biomarkers for CIPN. Real-time qPCR was used to measure mtDNA levels in whole blood collected from chemotherapy- and vehicle-treated rats at three key time-points of pain-like behaviour: prior to pain development, at the peak of mechanical hypersensitivity and at resolution of pain-like behaviour. Systemic oxaliplatin significantly increased mtDNA levels in whole blood prior to pain development. Furthermore, paclitaxel- and bortezomib-treated animals displayed significantly higher levels of mtDNA at the peak of mechanical hypersensitivity. Mitochondrial complex I activity in whole blood was assessed with an ELISA-based Complex I Enzyme Activity Dipstick Assay. Complex I activity was not altered by any of the three chemotherapeutic agents, either prior to or during pain-like behaviour. These data demonstrate that blood levels of mtDNA are altered after systemic administration of chemotherapy. Oxaliplatin, in particular, is associated with higher mtDNA levels before animals show any pain-like behaviour, thus suggesting a potential role for circulating mtDNA levels as non-invasive predictive biomarker for CIPN.

Nerve biopsy: Current indications and decision tools

After initial investigation of patients presenting with symptoms suggestive of neuropathy, a clinical decision is made for a minority of patients to undergo further assessment with nerve biopsy. Many nerve biopsies do not demonstrate a definitive pathological diagnosis and there is considerable cost and morbidity associated with the procedure. This highlights the need for appropriate selection of patients, nerves and neuropathology techniques. Additionally, concomitant muscle and skin biopsies may improve the diagnostic yield in some cases. Several advances have been made in diagnostics in recent years, particularly in genomics. The indications for nerve biopsy have consequently changed over time. This review explores the current indications for nerve biopsies and some of the issues surrounding its use. Also included are comments on alternative diagnostic modalities that may help to supplant or reduce the use of nerve biopsy as a diagnostic test. These primarily include extraneural biopsy and neuroimaging techniques such as magnetic resonance neurography and nerve ultrasound. Finally, we propose an algorithm to assist in deciding when to perform nerve biopsies.

Diagnostic challenges in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) consists of a spectrum of autoimmune diseases of the peripheral nerves, causing weakness and sensory symptoms. Diagnosis often is challenging, because of the heterogeneous presentation and both mis- and underdiagnosis are common. Nerve conduction study (NCS) abnormalities suggestive of demyelination are mandatory to fulfil the diagnostic criteria. On the one hand, performance and interpretation of NCS can be difficult and none of these demyelinating findings are specific for CIDP. On the other hand, not all patients will be detected despite the relatively high sensitivity of NCS abnormalities. The electrodiagnostic criteria can be supplemented with additional diagnostic tests such as CSF examination, MRI, nerve biopsy, and somatosensory evoked potentials. However, the evidence for each of these additional diagnostic tests is limited. Studies are often small without the use of a clinically relevant control group. None of the findings are specific for CIDP, meaning that the results of the diagnostic tests should be carefully interpreted. In this update we will discuss the pitfalls in diagnosing CIDP and the value of newly introduced diagnostic tests such as nerve ultrasound and testing for autoantibodies, which are not yet part of the guidelines.

Measuring conduction velocity distributions in peripheral nerves using neurophysiological techniques

OBJECTIVE

To determine how long it takes for neural impulses to travel along peripheral nerve fibers in living humans.

METHODS

A collision test was performed to measure the conduction velocity distribution of the ulnar nerve. Two stimuli at the distal and proximal sites were used to produce the collision. Compound muscle or nerve action potentials were recorded to perform the measurements on the motor or mixed nerve, respectively. Interstimulus interval was set at 1-5 ms. A quadri-pulse technique was used to measure the refractory period and calibrate the conduction time.

RESULTS

Compound muscle action potential produced by the proximal stimulation started to emerge at the interstimulus interval of about 1.5 ms and increased with the increment in interstimulus interval. Two groups of motor nerve fibers with different conduction velocities were identified. The mixed nerve showed a wider conduction velocity distribution with identification of more subgroups of nerve fibers than the motor nerve.

CONCLUSIONS

The conduction velocity distributions in high resolution on a peripheral motor and mixed nerve are different and this can be measured with the collision test.

SIGNIFICANCE

We provided ground truth data to verify the neuroimaging pipelines for the measurements of latency connectome in the peripheral nervous system.

Diagnostic Value of Sural Nerve Biopsy: Retrospective Analysis of Clinical Cases From 1981 to 2017

Nerve biopsy represents the conclusive step in the diagnostic work-up of peripheral neuropathies, and its diagnostic yield is still debated. The aim of this study is to consider the impact of nerve biopsy on reaching a useful diagnosis in different peripheral neuropathies and its changing over time. We retrospectively analyzed 1,179 sural nerve biopsies performed in the period 1981–2017 at Neurological Clinic of Policlinico San Martino (Genoa). We relied on medical records and collected both clinical and pathological data in a database. Biopsy provided univocal diagnoses in 53% of cases (with an increase over time), multiple diagnostic options in 14%, while diagnosis was undetermined in 33% (undetermined reports decreased during the years). In 57% of patients, the pre-biopsy suspicion was confirmed, while in 43% sural biopsy modified the clinical diagnosis. The highest yield was in axonal neuropathies (29% undetermined reports vs. 40% in demyelinating and 48% in mixed neuropathies). In 68% of patients with vasculitic neuropathy, this etiology was already suspected, whereas in 32% nerve biopsy modified the clinical diagnosis. During the years, the number of annually performed biopsies decreased significantly (p = 0.007), with an increase in the mean age of patients (p < 0.0001). The percentage of hereditary neuropathies had a significant decrease (p = 0.016), while the rate of vasculitic and chronic inflammatory neuropathies increased (p < 0.0001). This is the largest Italian study addressing the yield of sural nerve biopsy. During the years, we observed a progressive refinement of the indication of this procedure, which confirms its utility for interstitial neuropathies, particularly if non-systemic vasculitic neuropathy is suspected.

Incidental Ultrastructural Findings in the Sural Nerve and Dorsal Root Ganglion of Aged Control Sprague Dawley Rats in a Nonclinical Carcinogenicity Study

Xenobiotic-induced peripheral nerve damage is a growing concern. Identifying relative risks that a new drug may cause peripheral nerve injury over long periods of administration is gathering importance in the evaluation of animal models. Separating out age-related changes in peripheral nerves of rats caused by compression injury from drug-induced effects has been difficult. Biopsy of the sural nerve is utilized in humans for investigations of peripheral neuropathy, because it is largely removed from the effects of nerve compression. This study used transmission electron microscopy to identify incidental findings in the sural nerves and dorsal root ganglia of aged control rats over time. The goal was to establish a baseline understanding of the range of possible changes that could be noted in controls compared to rats treated with any new investigative drug. In this evaluation, most sural nerve fibers from aged control rats had few ultrastructural abnormalities of pathologic significance. However, glycogenosomes, polyglucosan bodies, swollen mitochondria, autolysosomes, split myelin, Schwann cell processes, and endoneural macrophages with phagocytosed debris (considered an indication of ongoing degenerative changes) were occasionally noted.

Technically successful ultrasound-guided percutaneous sural nerve needle biopsy in a patient with indeterminate peripheral neuropathy

OBJECTIVE

To determine whether ultrasound-guided percutaneous sural nerve needle biopsy yields sufficient tissue for analysis in a patient with suspected vasculitis-related peripheral neuropathy.

MATERIALS AND METHODS

With real-time ultrasound guidance, a hydrodissection of the sural nerve from the adjacent small saphenous vein was first performed. A 14-gauge biopsy needle was then manipulated under real-time ultrasound guidance to obtain two transverse samples of the sural nerve at the lateral distal calf.

RESULTS

The biopsy was technically successful and yielded adequate tissue for routine processing. The specimen showed mild epineurial perivascular chronic inflammation with marked loss of myelinated axons. These histologic findings are not diagnostically definitive for vasculitis-related peripheral neuropathy but were supportive of the diagnosis in combination with the patient's physical examination, laboratory, and electromyography findings. The patient suffered no immediate complications after the procedure.

CONCLUSIONS

This ultrasound-guided sural nerve needle biopsy, like many surgical biopsies, did not yield a definitive result in a patient with suspected vasculitis-related peripheral neuropathy; however, the procedure was technically successful. Given that percutaneous needle procedures offer many advantages over surgical procedures, we believe that this procedure warrants further investigation.

Mitochondrial dysfunction in the pathogenesis of chemotherapy-induced peripheral neuropathy

Several first-line chemotherapeutic agents, including taxanes, platinum agents and proteasome inhibitors, are associated with the dose-limiting side effect of chemotherapy-induced peripheral neuropathy (CIPN). CIPN predominantly manifests as sensory symptoms, which are likely due to drug accumulation within peripheral nervous tissues rather than the central nervous system. No treatment is currently available to prevent or reverse CIPN. The causal mechanisms underlying CIPN are not yet fully understood. Mitochondrial dysfunction has emerged as a major factor contributing to the development and maintenance of CIPN. This chapter will provide an overview of both clinical and preclinical data supporting this hypothesis. We will review the studies reporting the nature of mitochondrial dysfunction evoked by chemotherapy in terms of changes in mitochondrial morphology, bioenergetics and reactive oxygen species (ROS) generation. Furthermore, we will discuss the in vivo effects of pharmacological interventions that counteract chemotherapy-evoked mitochondrial dysfunction and ameliorate pain-like behavior.

IVIg for apparently autoimmune small-fiber polyneuropathy: first analysis of efficacy and safety

OBJECTIVES

Small-fiber polyneuropathy (SFPN) has various underlying causes, including associations with systemic autoimmune conditions. We have proposed a new cause; small-fiber-targeting autoimmune diseases akin to Guillain-Barré and chronic inflammatory demyelinating polyneuropathy (CIDP). There are no treatment studies yet for this 'apparently autoimmune SFPN' (aaSFPN), but intravenous immunoglobulin (IVIg), first-line for Guillain-Barré and CIDP, is prescribed off-label for aaSFPN despite very high cost. This project aimed to conduct the first systematic evaluation of IVIg's effectiveness for aaSFPN.

METHODS

With IRB approval, we extracted all available paper and electronic medical records of qualifying patients. Inclusion required having objectively confirmed SFPN, autoimmune attribution and other potential causes excluded. IVIg needed to have been dosed at ⩾1 g/kg/4 weeks for ⩾3 months. We chose two primary outcomes - changes in composite autonomic function testing (AFT) reports of SFPN and in ratings of pain severity - to capture objective as well as patient-prioritized outcomes.

RESULTS

Among all 55 eligible patients, SFPN had been confirmed by 3/3 nerve biopsies, 62% of skin biopsies, and 89% of composite AFT. Evidence of autoimmunity included 27% of patients having systemic autoimmune disorders, 20% having prior organ-specific autoimmune illnesses and 80% having ⩾1/5 abnormal blood-test markers associated with autoimmunity. A total of 73% had apparent small-fiber-restricted autoimmunity. IVIg treatment duration averaged 28 ± 25 months. The proportion of AFTs interpreted as indicating SFPN dropped from 89% at baseline to 55% (p ⩽ 0.001). Sweat production normalized (p = 0.039) and the other four domains all trended toward improvement. Among patients with pre-treatment pain ⩾3/10, severity averaging 6.3 ± 1.7 dropped to 5.2 ± 2.1 (p = 0.007). Overall, 74% of patients rated themselves 'improved' and their neurologists labeled 77% as 'IVIg responders'; 16% entered remissions that were sustained after IVIg withdrawal. All adverse events were expected; most were typical infusion reactions. The two moderate complications (3.6%) were vein thromboses not requiring discontinuation. The one severe event (1.8%), hemolytic anemia, remitted after IVIg discontinuation.

CONCLUSION

These results provide Class IV, real-world, proof-of-concept evidence suggesting that IVIg is safe and effective for rigorously selected SFPN patients with apparent autoimmune causality. They provide rationale for prospective trials, inform trial design and indirectly support the discovery of small-fiber-targeting autoimmune/inflammatory illnesses.

Diseases of the peripheral nerves

This chapter reviews the diseases of the peripheral nerves from a neuropathologic point of view, with a special focus on specific morphologic changes, and includes a summary of the histopathologic methods available for their diagnosis. As the rate of obesity and the prevalence of type 2 diabetes increase, diabetic neuropathy is the most common cause of peripheral neuropathy. Many systemic disorders with metabolic origin, like amyloidosis, hepatic failure, vitamin deficiencies, uremia, lipid metabolism disorders, and others, can also cause axonal or myelin alterations in the peripheral nervous system. The most notable causes of toxic neuropathies are chemotherapeutic agents, alcohol consumption, and exposure to heavy metals and other environmental or biologic toxins. Inflammatory neuropathies cover infectious neuropathies (Lyme disease, human immunodeficiency virus, leprosy, hepatitis) and neuropathies of autoimmune origin (sarcoidosis, Guillain-Barré syndrome/acute inflammatory demyelinating polyneuropathy, chronic inflammatory demyelinating polyneuropathy, and diverse forms of vasculitis. The increasing number of known diseases causing gene mutations in hereditary peripheral neuropathies requires precise characterization, which includes histopathology.

Drug therapy for chronic idiopathic axonal polyneuropathy

BACKGROUND

Chronic idiopathic axonal polyneuropathy (CIAP) is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, CIAP reduces quality of life. CIAP is diagnosed in 10% to 25% of people referred for evaluation of polyneuropathy. There is a need to gather and review emerging evidence on treatments, as the number of people affected is likely to increase in ageing populations. This is an update of a review first published in 2004 and previously updated in 2006, 2008, 2011 and 2013.

OBJECTIVES

To assess the effects of drug therapy for chronic idiopathic axonal polyneuropathy for reducing disability and ameliorating neurological symptoms and associated impairments, and to assess any adverse effects of treatment.

SEARCH METHODS

In July 2016, we searched Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews in the Cochrane Library, MEDLINE, Embase, and the Web of Science. We searched two trials registries for ongoing trials. We also handsearched the reference lists of relevant articles, reviews and textbooks identified electronically, and we would have contacted authors and other experts in the field to identify additional studies if this seemed useful.

SELECTION CRITERIA

We sought all randomised or quasi-randomised (alternate or other systematic treatment allocation) trials that examined the effects of any drug therapy in people with CIAP at least one year after the onset of treatment. People with CIAP had to fulfil the following criteria: age 40 years or older, distal sensory or sensorimotor polyneuropathy, absence of systemic or other neurological disease, chronic clinical course not reaching a nadir in less than two months, exclusion of any recognised cause of the polyneuropathy by medical history taking, clinical or laboratory investigations, and electrophysiological studies in agreement with axonal polyneuropathy, without evidence of demyelinating features. The primary outcome was the proportion of participants with a significant improvement in disability. Secondary outcomes were change in the mean disability score, change in the proportion of participants who make use of walking aids, change in the mean Medical Research Council sum score, degree of pain relief and/or reduction of other positive sensory symptoms, change in the proportion of participants with pain or other positive sensory symptoms, and frequency of adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed the results of the literature search and extracted details of trial methodology and outcome data of all potentially relevant trials.

MAIN RESULTS

We identified 39 studies and assessed them for possible inclusion in the review, but we excluded all of them because of insufficient quality or lack of relevance. We summarised evidence from non-randomised studies in the Discussion.

AUTHORS' CONCLUSIONS

Even though CIAP has been clearly described and delineated, no adequate randomised or quasi-randomised controlled clinical treatment trials have been performed. In their absence there is no proven efficacious drug therapy.

The intercostal nerve as a target for diagnostic biopsy

OBJECTIVE Peripheral nerve biopsy is a useful tool in diagnosing peripheral neuropathies. Sural and gracilis nerves have become the most common targets for nerve biopsy. However, the yield of sural nerve biopsy is limited in patients who have motor neuropathies, and gracilis nerve biopsy presents technical challenges and increased complications. The authors propose the intercostal nerve as an alternative motor nerve target for biopsy. METHODS A total of 4 patients with suspected peripheral neuropathies underwent intercostal nerve biopsy at the authors' institution. A rib interspace that is inferior to the pectoralis muscle and anterior to the anterior axillary line is selected for the procedure. Generally the lower intercostal nerves (i.e., T7-11) are targeted. An incision is made over the inferior aspect of the superior rib at the chosen interspace. Blunt dissection is carried down to the neurovascular bundle and the nerve is isolated, ligated, and cut to send for pathological examination. RESULTS The average operative time for all cases was 73 minutes, with average blood loss of 8 ml. Biopsy results from 1 patient exhibited axonopathy, and the other 3 patients demonstrated axonopathy with demyelination. There were no short- or long-term postoperative complications. None of the patients reported sensory or motor deficits related to the biopsy at 6 weeks postoperatively. CONCLUSIONS The intercostal nerve can be an alternative target for biopsy, especially in patients with predominantly motor neuropathies, due to its mixed sensory and motor fibers, straightforward anatomy, minimal risk of serious sensory deficits, and no risk of motor impairment.

Pediatric Nerve Biopsy Diagnostic and Treatment Utility in Tertiary Care Referral

BACKGROUND

Pediatric neuropathies are both unique and similar to their adult counterparts, with genetic varieties thought to be more common. The objective of this work was to assess the utility of nerve biopsy in children at a tertiary referral center in light of availability of current genetic testing.

METHODS

We retrospectively reviewed the clinical, nerve biopsy, and genetic testing findings of 316 pediatric (age ≤18 years) patients.

RESULTS

Median age at diagnosis was 9.8 years (4 days to 18 years). Nerve biopsy was nontargeted in 198 (182 whole sural, seven superficial peroneal, and nine other), targeted in 21 (14 fascicular sciatic and seven brachial plexus), and unknown in 97 cases. Prebiopsy localizations and diagnoses were diverse, most commonly with length-dependent localizations (n = 150). Median follow-up was 6 months (0 to 480 months). A distinctive histopathologic diagnosis was made in 106 cases (33%), including inflammatory or immune (n = 30), neoplastic (n = 19), hereditary (n = 41), vasculitis (n = 10), and other (n = 6). Nerve biopsy confirmed the suspected diagnosis in 91 (29%) individuals and changed or refined the initial diagnosis in 182 (58%). Treatment modifications as a result of biopsy occurred in 80 (25%) cases; 59 (19% of the entire cohort) with clinical improvements noted, most commonly by immunotherapy (n = 30). Low diagnostic yield occurred in "hypotonic infants" without nerve conduction abnormalities. Pain at the biopsy site beyond 1 month was rare (n = 3; 1%). Forty-four patients underwent genetic testing. Among demyelinating varieties, mutations were identified in five of 11 (46%) cases compared with only six of 33 (18%) cases of axonal varieties.

CONCLUSION

Pediatric nerve biopsy provides diagnostic information that frequently alters treatment recommendations. Furthermore, it leads to clinical improvements, especially in inflammatory immune neuropathies. For suspected inherited varieties, genetic testing has the highest diagnostic yield in demyelinating phenotypes.

Targeted fascicular biopsy of the sciatic nerve and its major branches: rationale and operative technique

OBJECT

Nerve biopsy is typically performed in distal, noncritical sensory nerves without using imaging to target the more involved regions. The yield of these procedures rarely achieves more than 50%. In selected cases where preoperative evaluation points toward a more localized (usually a more proximal) process, targeted biopsy would likely capture the disease. Synthesis of data obtained from clinical examination, electrophysiological testing, and MRI allows biopsy of a portion of the major mixed nerves safely and efficiently. Herein, experiences with the sciatic nerve are reported and a description of the operative technique is provided.

METHODS

All cases of sciatic nerve biopsy performed between 2000 and 2014 were reviewed. Only cases of fascicular nerve biopsy approached from the buttock or the posterior aspect of the thigh were included. Demographic data, clinical presentation, and the presence of percussion tenderness for each patient were recorded. Reviewed studies included electrodiagnostic tests and imaging. Previous nerve and muscle biopsies were noted. All details of the procedure, final pathology, and its treatment implications were recorded. The complication rate was carefully assessed for temporary as well as permanent complications.

RESULTS

One hundred twelve cases (63 men and 49 women) of sciatic nerve biopsy were performed. Mean patient age was 46.4 years. Seventy-seven (68.8%) patients presented with single lower-extremity symptoms, 16 (14.3%) with bilateral lower-extremity symptoms, and 19 (17%) with generalized symptoms. No patient had normal findings on physical examination. All patients underwent electrodiagnostic studies, the findings of which were abnormal in 110 (98.2%) patients. MRI was available for all patients and was read as pathological in 111 (99.1%). The overall diagnostic yield of biopsy was 84.8% (n = 95). The pathological diagnoses included inflammatory demyelination, perineurioma, nonspecific inflammatory changes, neurolymphomatosis, amyloidosis, prostate cancer, injury neuroma, neuromuscular choristoma, sarcoidosis, vasculitis, hemangiomatosis, arteriovenous malformation, fibrolipomatous hamartoma (lipomatosis of nerve), and cervical adenocarcinoma. The series included 11 (9.9%) temporary and 5 (4.5%) permanent complications: 3 patients (2.7%) reported permanent numbness in the peroneal division distribution, and 2 patients (1.8%) were diagnosed with neuromuscular choristoma that developed desmoid tumor at the biopsy site 3 and 8 years later.

CONCLUSIONS

Targeted fascicular biopsy of the sciatic nerve is a safe and efficient diagnostic procedure, and in highly selected cases can be offered as the initial procedure over distal cutaneous nerve biopsy. Diagnoses were very diverse and included entities considered very rare. Even for the more prevalent diagnoses, the biopsy technique allowed a more targeted approach with a higher diagnostic yield and justification for more aggressive treatment. In this series, new radiological patterns of some entities were identified, which could be biopsied less frequently.

Etiologic spectrum of biopsy-proven peripheral neuropathies in childhood from a resource-poor setting

There are only a few studies describing the etiologic spectrum of biopsy-proven peripheral neuropathies in children. This study reviewed the clinical, electrophysiological, and pathologic profile of 239 children (≤18 years of age) who have undergone nerve biopsy in a tertiary care centre for neurologic disorders and analyzed the etiologic spectrum and utility of nerve biopsy. The clinical profile, neuropathologic findings, and other investigations were combined to infer the final diagnosis. Neuropathy was detected in 199 biopsies; axonal pathology in 43%; demyelination in 41%; mixed pattern in 8%; and nonspecific findings in 8%. The major diagnostic categories included hereditary neuropathies (48%), heredodegenerative and metabolic disorders (27%), and inflammatory neuropathies (12%). Nerve biopsy proved most helpful in diagnosis of demyelinating and inflammatory neuropathies, reiterating its usefulness in specific situations.

Neuropathy in elderly: lessons learnt from nerve biopsy

OBJECTIVE

To study the utility of nerve biopsy in providing diagnostic, therapeutic or prognostic information that aid in clinical management in elderly subjects with peripheral neuropathy.

METHODS

Clinico-pathological data of 100 elderly subjects aged 65 and above with peripheral neuropathy who underwent nerve biopsy in the last decade (2002-2011) was reviewed.

RESULTS

The study included 100 subjects (M:F 78:22). Mean age at biopsy and symptom duration was 69.62±4.8 years and 24.17±40.4 months, respectively. The most common pattern of was distal symmetric sensorimotor polyneuropathy (35%), followed by multiple mononeuropathy (29%) and asymmetric sensorimotor neuropathy (15%). The nerve biopsy was 'diagnostic' in 24%, (definite vasculitis in 12, leprosy in 10 and acute inflammatory demyelinating polyradiculoneuropathy in 2) and proved 'essential' or 'helpful' in therapeutic management in 81% subjects. In 60 (60%) patients, where a pre-biopsy aetiological diagnosis could be arrived at based on the available data, nerve biopsy confirmed the diagnosis in 29 of 60 (48.3%), and offered a new diagnosis in 25 (41.7%). A higher yield of biopsy was noted in subjects with asymmetric/multiple mononeuropathy compared with symmetric neuropathies (32.7% versus 17.7%). In 40 (40%) patients without a pre-biopsy aetiological diagnosis, nerve biopsy was 'essential' in 7 of 40 (17.5%) as it provided a definitive diagnosis (definite vasculitis: 5, leprosy: 2), and 'helpful' in 21 of 40 (52.5%) (ischaemic neuropathy: 10, possible vasculitis: 9, probable vasculitis: 2).

CONCLUSION

Nerve biopsy aided in the detection of potentially treatable disorders and influenced patient management in a significant proportion of elderly subjects with peripheral neuropathy (81%), particularly in subset with undiagnosed neuropathies confirming that it's a useful tool in diagnosis of neuropathy in the elderly. With minor differences, the aetiological profile in our biopsied neuropathic elderly subjects may reflect the findings in other similar cohorts.

Structural and functional assessment of skin nerve fibres in small-fibre pathology

Damage to nociceptor nerve fibres may give rise to peripheral neuropathies, some of which are pain free and some are painful. A hallmark of many peripheral neuropathies is the loss of small nerve fibres in the epidermis, a condition called small-fibre neuropathy (SFN) when it is predominantly the small nerve fibres that are damaged. Historically, SFN has been very difficult to diagnose as clinical examination and nerve conduction studies mainly detect large nerve fibres, and quantitative sensory testing is not sensitive enough to detect small changes in small nerve fibres. However, taking a 3-mm punch skin biopsy from the distal leg and quantification of the nerve fibre density has proven to be a useful method to diagnose SFN. However, the correlation between the nerve fibre loss and other test results varies greatly. Recent studies have shown that it is possible not only to extract information about the nerve fibre density from the biopsies but also to get an estimation of the nerve fibre length density using stereology, quantify sweat gland innervation and detect morphological changes such as axonal swelling, all of which may be additional parameters indicating diseased small fibres relating to symptoms reported by the patients. In this review, we focus on available tests to assess structure and function of the small nerve fibres, and summarize recent advances that have provided new possibilities to more specifically relate structural findings with symptoms and function in patients with SFN.

Muscle and nerve biopsies: techniques for the neurologist and neurosurgeon

OBJECTIVE

Muscle and nerve biopsies are commonly performed procedures for the diagnosis of neuromuscular disorders. Neurologists and neurosurgeons are often consulted to perform these procedures in clinical practice. We provide guidelines in the performance of muscle and nerve biopsies.

METHODS

We describe the technique for performance of muscle and nerve biopsy, and review the relevant literature.

RESULTS

The quadriceps muscle is the most typical biopsy site for most myopathies, whereas the sural nerve is the most common nerve biopsy site for most peripheral neuropathies. Other sites may be utilized depending upon the pattern of symptoms or the differential diagnosis. Motor nerves may be sampled in the setting of motor neuron disease, for example. We advocate the use of conduit repair to allow for sensory or motor recovery to occur following nerve biopsy.

CONCLUSION

The muscle biopsy and nerve biopsy may be performed with high yield, low morbidity, and rare complications.

The nerve biopsy: indications, technical aspects, and contribution

This chapter discusses the indications for biopsying a peripheral nerve and the factors involved in justifying this decision and then deciding which nerve to take. There is a table summarizing some of the causes of neuropathy and attempting to relate these to the probability that nerve biopsy would be helpful in diagnosis. The surgical procedure for the nerve biopsy is described including aftercare and possible complications. The techniques involved in processing and staining the nerve are discussed. This section includes the possibilities of creating artefactual damage by mishandling or poor technique, and how to avoid these. Modification to the standard resin processing schedule to allow the teasing out of individual nerve fibers is briefly described, as are methods for measuring fiber density, fiber size and myelin thickness. There is also a brief discussion of the applications of immunohistochemistry. This is followed by a section on interpretation by light and electron microscopy in which some of the more important diagnostic features are described and illustrated, as are nonspecific morphological findings. Interpretation of teased fiber preparations is discussed. Finally, some common causes of incorrect interpretation are mentioned.

Diabetic somatic neuropathy

Diabetic neuropathy (DN) is the most common, most neglected and difficult to treat diabetic complication. It affects the whole body, and presents with diverse clinical pictures. The most important outcome of somatic and autonomic DN are the development of diabetic foot followed by diabetic ulceration and possible amputation. In this chapter the definition, epidemiology, pathophysiology and classification of somatic DN will be discussed. Attention will be given to various practical aspects of somatic DN of different types with their specific clinical presentation, diagnostic approaches and treatment options, including the usually rarely discussed gender differences. DN remains a problem in diabetology, compared to other micro- and macrovascular complications. The disease is rarely investigated, although simple testing devices for somatic nerve impairment exist, and remains difficult to treat because ofthe complex pathogenetic mechanisms. The main prevention/progression delaying measure for the progression of DN is the tight glycaemic control. Painful DN is common and need appropriate symptomatic relieving drugs. Future investigations must be targeted on new treatment options.

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.

Nerve biopsy--some comments on procedures and indications

Nerve biopsy is most often a final step in the evaluation of patients with peripheral neuropathy. The procedure should always be expected to result in varying degree of sensory loss within the innervation area of the biopsied nerve and chronic pain in the area may also occur. Therefore appropriate informed consent must be obtained and a weighing of such side effects and benefits for the patient, particularly therapeutical consequences, should be seriously considered before the procedure is performed. The surgical procedure and the processing in the laboratory of the nerve material must hold a high standard at all levels. Nerve biopsy should not be performed before adequate clinical, electrophysiological and laboratory investigations have been performed. The choice of nerve is important, but in most instances the sural nerve is biopsied, although the superficial peroneal nerve is also an option and allows an easy access to muscle biopsy in the same procedure. Laboratories performing nerve biopsies should have the facilities and expertise to prepare and evaluate fixed and frozen sections (paraffin, cryostat and epoxy-sections) and teased fibers, and also to perform light and electron microscopy and immunohistochemistry. Although not routinely used, the option of morphometry should be available as well. We recommend that properly trained technicians start the processing procedures in the operating room and, if feasible, even in hospitals outside that of the hospital with nerve laboratory. We also prefer routine use of teased fiber analysis as this visualizes in an excellent way pathological processes like axonal degeneration, demyelination and remyelination as well as other features. Evaluation of small fiber neuropathy is rarely an indication for nerve biopsy and should be investigated with skin biopsy and visualization and quantification of intraepidermal nerve fibers. Investigation of inflammatory neuropathy, particularly to demonstrate nerve vasculitis, is the main indication of nerve biopsy.

Nerve biopsy: requirements for diagnosis and clinical value

In many instances, nerve biopsy is not necessary in the diagnostic work-up of a peripheral neuropathy. However, histological examination of a tissue sample is still mandatory to show specific lesions in various conditions involving peripheral nerves. As there are fewer laboratories that examine human nerve samples, practitioners including neurologists and general pathologists may not be completely aware of the technical issues and data that are provided by nerve biopsy. Nerve biopsy is considered an invasive diagnostic method, although, its complications are by far less disabling than most of the disorders that lead to its indications. Nevertheless, the decision to perform a nerve biopsy has to be made on a case-by-case basis, and its results must be discussed between the pathologist and the clinician who is in charge of the patient's care. In this paper, we review the minimal technical requirements for proper peripheral nerve tissue analysis. Moreover, we provide data on the usefulness of nerve biopsy in various situations including abnormal deposits, cell infiltrates, link between peripheral neuropathy and monoclonal gammopathy, and numerous hereditary disorders.

Usefulness of labial salivary gland biopsy in familial amyloid polyneuropathy Portuguese type

BACKGROUND

The diagnosis of amyloidosis of all types is definitively made by demonstration of Congo red binding material in the affected tissues. Nerve biopsy was classically used to diagnose amyloid polyneuropathy but less invasive alternative types of biopsies have been proposed including labial salivary gland (LSG) biopsy, a minimally invasive procedure.

METHOD

LSG biopsies were done in 87 subjects with molecular diagnosis of TTRVal30Met mutation. The group includes 76 patients in different stages of familial amyloid polyneuropathy and 11 asymptomatic carriers. They were all submitted to a stomatological and a neurological observation to evaluate oral health problems and to determine the neurological stage of the disease. No major oral health problems were found. Mean age of onset of the symptomatic disease was 32.8 years (+/-9.69 SD).

CONCLUSIONS

No significant side effects occurred after the surgical procedure, and adequate material for pathological analysis was always obtained. Amyloid deposition was found in 91% of the patients. Patients with negative biopsies (N = 7) were all in the earlier stage of the disease. Two asymptomatic carriers had biopsies with amyloid deposition. We conclude that LSG biopsy is a useful, sensitive and minimal invasive method to detect amyloid deposition.

Practice parameter: the evaluation of distal symmetric polyneuropathy: the role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review). Report of the American Academy of Neurology, the American Association of Neuromuscular and Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation

BACKGROUND

Distal symmetric polyneuropathy (DSP) is the most common variety of neuropathy. Since the evaluation of this disorder is not standardized, the available literature was reviewed to provide evidence-based guidelines regarding the role of autonomic testing, nerve biopsy and skin biopsy for the assessment of polyneuropathy.

METHODS

A literature review using MEDLINE, EMBASE, Science Citation Index and Current Contents was performed to identify the best evidence regarding the evaluation of polyneuropathy published between 1980 and March 2007. Articles were classified according to a four-tiered level of evidence scheme and recommendations were based upon the level of evidence.

RESULTS AND CONCLUSIONS

1. Autonomic testing may be considered in the evaluation of patients with polyneuropathy to document autonomic nervous system dysfunction (Level B). Such testing should be considered especially for the evaluation of suspected autonomic neuropathy (Level B) and distal small fiber sensory polyneuropathy (SFSN) (Level C). A battery of validated tests is recommended to achieve the highest diagnostic accuracy (Level B). 2. Nerve biopsy is generally accepted as useful in the evaluation of certain neuropathies as in patients with suspected amyloid neuropathy, mononeuropathy multiplex due to vasculitis, or with atypical forms of chronic inflammatory demyelinating polyneuropathy (CIDP). However, the literature is insufficient to provide a recommendation regarding when a nerve biopsy may be useful in the evaluation of DSP (Level U). 3. Skin biopsy is a validated technique for determining intraepidermal nerve fiber (IENF) density and may be considered for the diagnosis of DSP, particularly SFSN (Level C). There is a need for additional prospective studies to define more exact guidelines for the evaluation of polyneuropathy.

An update on nerve biopsy

Indications for nerve biopsy have decreased during the last 20 years. For the most part, this is a result of progress in the application of molecular biologic diagnostic testing for genetic peripheral neuropathies (PNs) and the increasing use of skin biopsy. The latter is primarily used to evaluate small-fiber PN, although it rarely discloses the specific etiology of a PN. Nerve biopsies are usually performed on either the sural or the superficial peroneal nerve, the latter in combination with removal of portions of the peroneus brevis muscle. The definite diagnosis of vasculitic lesions can be readily established on small paraffin-embedded nerve biopsy samples, although in some cases, the characteristic lesions are only apparent in muscle specimens. Other nerve specimens are routinely fixed in buffered glutaraldehyde and prepared for semithin sections and electron microscopy; frozen specimens are used for immunofluorescence studies. Electron microscopy is of great value in some cases of chronic inflammatory demyelinating polyneuropathies, monoclonal gammopathy, and storage diseases. Because more than 30 genes may be involved in genetic PNs, analysis of nerve lesions can direct the search for mutations in specific genes. Electron microscopy immunocytochemistry is mandatory in some cases of monoclonal dysglobulinemia. Thus, nerve biopsy is still of value in specific circumstances when it is performed by trained physicians and examined in a laboratory with expertise in nerve pathology.

POLYNEUROPATHIES IN THE ELDERLY: A CLINICO PATHOLOGICAL STUDY OF 74 CASES

In elderly patients, peripheral neuropathies are common and may lead to disability. In order to investigate the relative incidence of different polyneuropathies in the elderly focusing on the contribution of nerve biopsy to their diagnosis, the authors studied 74 patients over 65 years of age with clinical, laboratory, electrophysiological, and sural nerve biopsy findings of different types of polyneuropathy. Vasculitic polyneuropathy seemed to be the most common cause of disabling neuropathy in the elderly, followed by paraneoplasia and diabetes. The possible diagnosis of idiopathic axonal neuropathy in the nine cases with neuropathy of unknown origin is discussed.

Usefulness of sural nerve biopsy in the genomic era

The value of peripheral nerve biopsy is now sometimes questioned due to the high complication rate and the recent development of noninvasive molecular techniques for diagnosis of hereditary neuropathy. However, the disorders that can be diagnosed by genetic analysis are limited and sural nerve biopsy is still a powerful tool for making a correct diagnosis of peripheral neuropathy. Histological evaluation of the sural nerve has long focused on changes of the two major components of peripheral nerves, axons and myelin, as well as on the detection of diagnostic changes such as amyloid deposits, sarcoid tubercles, and vasculitis. In addition to these components, the sural nerve biopsy specimen contains various important cells, including perineurial cells, mast cells, endothelial cells, pericytes, and lymphocytes. Among these cells, the endothelial cells and pericytes form the blood-nerve barrier (BNB) and investigation of these cells can reveal important information, especially in inflammatory neuropathies. To better understand the biological basis of BNB, we established rat and human immortal cell lines from the endothelial cells and pericytes of endoneurial microvessels. Characterization of these cell lines is now underway at our laboratory. These BNB cell lines should provide useful information concerning the pathophysiology of peripheral neuropathy, and we should obtain a new perspective for the investigation of nerve biopsy specimens after understanding the molecular background of the BNB.

Evaluation of distal symmetric polyneuropathy: the role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review)

Distal symmetric polyneuropathy (DSP) is the most common variety of neuropathy. Since the evaluation of this disorder is not standardized, the available literature was reviewed to provide evidence-based guidelines regarding the role of autonomic testing, nerve biopsy, and skin biopsy for the assessment of polyneuropathy. A literature review using MEDLINE, EMBASE, Science Citation Index, and Current Contents was performed to identify the best evidence regarding the evaluation of polyneuropathy published between 1980 and March 2007. Articles were classified according to a four-tiered level of evidence scheme and recommendations were based on the level of evidence. (1) Autonomic testing may be considered in the evaluation of patients with polyneuropathy to document autonomic nervous system dysfunction (Level B). Such testing should be considered especially for the evaluation of suspected autonomic neuropathy (Level B) and distal small fiber sensory polyneuropathy (SFSN) (Level C). A battery of validated tests is recommended to achieve the highest diagnostic accuracy (Level B). (2) Nerve biopsy is generally accepted as useful in the evaluation of certain neuropathies as in patients with suspected amyloid neuropathy, mononeuropathy multiplex due to vasculitis, or with atypical forms of chronic inflammatory demyelinating polyneuropathy (CIDP). However, the literature is insufficient to provide a recommendation regarding when a nerve biopsy may be useful in the evaluation of DSP (Level U). (3) Skin biopsy is a validated technique for determining intraepidermal nerve fiber (IENF) density and may be considered for the diagnosis of DSP, particularly SFSN (Level C). There is a need for additional prospective studies to define more exact guidelines for the evaluation of polyneuropathy.

Peripheral neuropathy

Patients presenting with symptoms of peripheral neuropathy are commonplace in the practice of generalist physicians, office based or hospitalists. Although there are at least a thousand different causes for peripheral neuropathy, the majority of patients can be properly diagnosed (and managed) based on framing the diagnostic possibilities within one of six typical scenarios. The case presentations in this article illustrate common and less common but essential presentations and the approach to evaluation and treatment. For these patients the key to success lies in the history and clinical examination findings.

Biopsy of the posterior interosseous nerve: a low morbidity method for assessment of peripheral nerve disorders

AIMS

The sural nerve is the commonest peripheral nerve biopsied to help in the diagnosis of peripheral neuropathy of unknown cause. However, associated complications limit its use. The aim was, as an alternative, to asses biopsy of the terminal branch of the posterior interosseous nerve (PIN) in the forearm.

METHODS

PIN pathology was morphometrically quantified in 10 male patients with Type 2 diabetes and compared with six PIN biopsy specimens taken post mortem from male cadavers with no history of neuropathy or trauma.

RESULTS

The PIN biopsy procedure provides a long (approximately 3 cm) mono- or bifascicular nerve biopsy with generous epineurial tissue and adjacent vessels. Our results show a significantly lower myelinated fibre density in subjects with diabetes [5782 (3332-9060)/mm(2)] compared with autopsy control material [9256 (6593-12,935)/mm(2), P < 0.007]. No postoperative discomfort or complications were encountered.

CONCLUSIONS

A reduction in myelinated fibre density has previously been shown to be a clinically meaningful measure of neuropathy in diabetic patients. We demonstrate similar findings using the PIN biopsy. The PIN biopsy procedure fulfils the criteria for nerve biopsy and was well tolerated by the patients. It may be a possible alternative to sural nerve biopsy to allow for diagnosis of neuropathy.

Sequelae following sural nerve biopsy in type 1 diabetic subjects

OBJECTIVES

To detect post-operative sequelae of sural nerve biopsy.

MATERIALS AND METHODS

A questionnaire mailed to type 1 diabetic patients (n = 24; male/female 23/1; reply n = 23) 2 years after biopsy.

RESULTS

Type 1 diabetic patients (age 56 [11]; median [interquartile range]) had a long duration of diabetes (DM; 20 [19] years) and all had neuropathy. Three out of 24 patients developed infection (two superficial and one deep) and one had a post-operative bleeding. Less frequent pain among the patients were reported from one centre. About one-third or more of the patients still complained of pain, mostly mild, in the biopsy area and paraesthesia in the foot 2 years after surgery. More than two-thirds of the patients were reluctant for further biopsy; a crucial information in drug trial planning.

CONCLUSIONS

Sequelae of a sural nerve biopsy occur in type 1 DM. The risk for wound infections should be considered.

Complications following sural and peroneal nerve biopsies

Nerve biopsy is used as part of the investigation of patients with peripheral neuropathy and is particularly useful in confirming the diagnosis of peripheral nerve vasculitis. Previous studies have suggested that sampling the peroneal nerve, in combination with peroneus brevis, is more sensitive than the sural nerve for this diagnosis but there are no published data on the complication rate of peroneal nerve biopsies. We have assessed the complications in 50 patients undergoing nerve biopsy, and have shown that although biopsy of the peroneal nerve may result in a larger area of sensory loss in some patients, other complications are not increased when compared with sural nerve biopsy.

Functional and morphological effects of repeated sodium arsenite exposure on rat peripheral sensory nerves

Exposure to inorganic arsenic (iAs) is known to result in peripheral neuropathy. To better understand the functional and morphological consequences of iAs exposure, we examined the electrophysiological and histological characteristics of the sensory sural nerves in adult Male Wistar rats following 30 days of sodium arsenite administration by gavage (10 mg/kg body weight/day). Arsenic (As) levels in the peripheral nerves of exposed animals were about 150 times greater than those in controls. Lipid peroxidation was also increased in iAs-exposed animals. Compound action potentials (CAPs) evoked in iAs-exposed nerves were characterized by a slower conduction velocity ( approximately 26%). iAs-exposed nerves also showed a trend towards a decreased CAP area ( approximately 35%). These electrophysiological changes were consistent with histological alterations such as a approximately 56% decrease in myelin thickness. In addition, the perimeter and transverse area of axons were reduced to 29% and 45% of control, respectively. Our results suggest that accumulation of As produced by iAs exposure induces oxidative damage, severe demyelination, and other morphological alterations in axons of peripheral nerves. These changes may, in turn, induce changes in the generation and propagation of action potentials in peripheral nerves, leading to decreased transmission of information from peripheral sensory organs to the central nervous system.