Diagnostic and therapeutic value due to suspected diagnosis, long-term complications, and indication for 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.

Peripheral Neuropathy

Peripheral neuropathy is a commonly encountered diagnosis in both neurology and primary care office settings. It is important for primary care providers to identify, characterize, and diagnose patients with neuropathy. This study aims to describe the clinical presentation, diagnostic work up, and treatment options for this entity, as well as the identification of atypical features that should prompt specialized laboratory testing, electrodiagnostic testing, and neurologic consultation.

What is new in intraneural perineurioma?

Since the initial description of intraneural (IN) perineurioma in 1964, advances in the understanding of the clinical presentation, diagnostic imaging, pathologic features, and genetic underpinnings have changed how this pathology is managed. IN perineuriomas are rare, benign peripheral nerve sheath tumors, most frequently coming to clinical attention when patients present with painless, progressive weakness or sensory loss in adolescence or young adulthood. The gold standard of diagnosis has traditionally been with targeted tissue biopsy demonstrating "pseudo-onion bulb" formation with positive epithelial membrane antigen (EMA) staining. However, modern magnetic resonance imaging is allowing some patients to forgo biopsy. Recent genetic studies of IN perineuriomas have demonstrated common TRAF7 point mutations and rare NF2 mutations, which may present targets for diagnosis or therapy in the future. Current advances have allowed for us to provide improved patient counseling with informed understanding for various clinical scenarios. With the workup and diagnosis now clearly defined, the next frontier is for improving the lives of patients with IN perineuriomas through the interaction between restoration of functional deficits and advances in our understanding of the genetics of this entity.

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.

The role of sural nerve biopsy in diagnosis of vasculitis

OBJECTIVE

The diagnostic yield of sural nerve biopsy (SNB) in vasculitis is uncertain. Our aim was to document relevant characteristics of patients undergoing sural nerve biopsy in the investigation of vasculitis; determine the diagnostic yield; relate positive biopsy findings to patient demographic, laboratory, and clinical parameters; and to calculate the rate of surgical complications.

METHODS

Patients with suspected vasculitis that underwent SNB as part of diagnostic evaluation at academic medical centres in Sweden and the United Kingdom were identified by searching local pathology databases and clinic registers. A structured review of medical case records and pathology reports was conducted. Histological findings were categorized as definite, probable, or no vasculitis in accordance with the 2015 Brighton Collaboration reinterpretation and update of the Peripheral Nerve Society Guidelines for Vasculitic Neuropathy. Definite and probable findings were considered positive for vasculitis.

RESULTS

Ninety-one patients that underwent SNB were identified (45% female). Forty (44%) showed histological evidence of vasculitis: 14 definite and 26 probable. A concomitant muscle biopsy conducted in 10 patients did not contribute to the diagnostic yield. Positive antineutrophil cytoplasmic antibody test, organ involvement other than the nervous system, and a longer biopsy sample were associated with a positive biopsy. The reported surgical complication rate was 15%.

CONCLUSION

Sural nerve biopsy of sufficient length is an expedient procedure to confirm a diagnosis of vasculitis.

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.

Approach to Peripheral Neuropathy for the Primary Care Clinician

Peripheral neuropathy is commonly encountered in the primary care setting and is associated with significant morbidity, including neuropathic pain, falls, and disability. The clinical presentation of neuropathy is diverse, with possible symptoms including weakness, sensory abnormalities, and autonomic dysfunction. Accordingly, the primary care clinician must be comfortable using the neurologic examination-including the assessment of motor function, multiple sensory modalities, and deep tendon reflexes-to recognize and characterize neuropathy. Although the causes of peripheral neuropathy are numerous and diverse, careful review of the medical and family history coupled with limited, select laboratory testing can often efficiently lead to an etiologic diagnosis. This review offers an approach for evaluating suspected neuropathy in the primary care setting. It will describe the most common causes, suggest an evidence-based workup to aid in diagnosis, and highlight recent evidence that allows for selection of symptomatic treatment of patients with neuropathy.

Targeted fascicular biopsy of the brachial plexus: rationale and operative technique

OBJECTIVE

Nerve biopsy is useful in the management of neuromuscular disorders and is commonly performed in distal, noncritical cutaneous nerves. In general, these procedures are diagnostic in only 20%–50%. In selected cases in which preoperative evaluation points toward a more localized process, targeted biopsy would likely improve diagnostic yield. The authors report their experience with targeted fascicular biopsy of the brachial plexus and provide a description of the operative technique.

METHODS

All cases of targeted biopsy of the brachial plexus biopsy performed between 2003 and 2015 were reviewed. Targeted nerve biopsy was performed using a supraclavicular, infraclavicular, or proximal medial arm approach. Demographic data and clinical presentation as well as the details of the procedure, adverse events (temporary or permanent), and final pathological findings were recorded.

RESULTS

Brachial plexus biopsy was performed in 74 patients (47 women and 27 men). The patients' mean age was 57.7 years. All patients had abnormal findings on physical examination, electrodiagnostic studies, and MRI. The overall diagnostic yield of biopsy was 74.3% (n = 55). The most common diagnoses included inflammatory demyelination (19), breast carcinoma (17), neurolymphomatosis (8), and perineurioma (7). There was a 19% complication rate; most of the complications were minor or transient, but 4 patients (5.4%) had increased numbness and 3 (4.0%) had additional weakness following biopsy.

CONCLUSIONS

Targeted fascicular biopsy of the brachial plexus is an effective diagnostic procedure, and in highly selected cases should be considered as the initial procedure over nontargeted, distal cutaneous nerve biopsy. Using MRI to guide the location of a fascicular biopsy, the authors found this technique to produce a higher diagnostic yield than historical norms as well as providing justification for definitive treatment.

MRI of pathology-proven peripheral nerve amyloidosis

OBJECTIVE

To highlight the MRI characteristics of pathologically proven amyloidosis involving the peripheral nervous system (PNS) and determine the utility of MRI in directing targeted biopsy for aiding diagnosis.

MATERIALS AND METHODS

A retrospective study was performed for patients with pathologically proven PNS amyloidosis who also underwent MRI of the biopsied or excised nerve. MRI signal characteristics, nerve morphology, associated muscular denervation changes, and the presence of multifocal involvement were detailed. Pathology reports were reviewed to determine subtypes of amyloid. Charts were reviewed to gather patient demographics, neurological symptoms and radiologist interpretation.

RESULTS

Four men and three women with a mean age of 62 ± 11 years (range 46-76) were identified. All patients had abnormal findings on EMG with mixed sensorimotor neuropathy. All lesions demonstrated diffuse multifocal neural involvement with T1 hypointensity, T2 hyperintensity, and variable enhancement on MRI. One lesion exhibited superimposed T2 hypointensity. Six of seven patients demonstrated associated muscular denervation changes.

CONCLUSION

Peripheral nerve amyloidosis is rare, and the diagnosis is difficult because of insidious symptom onset, mixed sensorimotor neurologic deficits, and the potential for a wide variety of nerves affected. On MRI, peripheral nerve involvement is most commonly characterized by T1 hypointensity, T2 hyperintensity, variable enhancement, maintenance of the fascicular architecture with fusiform enlargement, multifocal involvement and muscular denervation changes. While this appearance mimics other inflammatory neuropathies, MRI can readily detect neural changes and direct-targeted biopsy, thus facilitating early diagnosis and appropriate management.

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.

Towards instantaneous cellular level bio diagnosis: laser extraction and imaging of biological entities with conserved integrity and activity

The prospect for spatial imaging with mass spectroscopy at the level of the cell requires new means of cell extraction to conserve molecular structure. To this aim, we demonstrate a new laser extraction process capable of extracting intact biological entities with conserved biological function. The method is based on the recently developed picosecond infrared laser (PIRL), designed specifically to provide matrix-free extraction by selectively exciting the water vibrational modes under the condition of ultrafast desorption by impulsive vibrational excitation (DIVE). The basic concept is to extract the constituent protein structures on the fastest impulsive limit for ablation to avoid excessive thermal heating of the proteins and to use strongly resonant 1-photon conditions to avoid multiphoton ionization and degradation of the sample integrity. With various microscope imaging and biochemical analysis methods, nanoscale single protein molecules, viruses, and cells in the ablation plume are found to be morphologically and functionally identical with their corresponding controls. This method provides a new means to resolve chemical activity within cells and is amenable to subcellular imaging with near-field approaches. The most important finding is the conserved nature of the extracted biological material within the laser ablation plume, which is fully consistent with in vivo structures and characteristics.

Contribution of the sural nerve to postural stability and cutaneous sensation of the lower limb

BACKGROUND

The sural nerve is a cutaneous nerve of the lower limb that innervates the posterolateral aspect of the lower leg, ankle, and foot. Considering this pattern, it is plausible that it contributes to the maintenance of postural stability. However, the implications of sensory loss following sural nerve injury have yet to be thoroughly investigated. Therefore, the aim of this study was to investigate the immediate effect of sural nerve sensory loss on postural stability and its variability of innervation to the lower limb.

METHODS

Twenty-five healthy adult subjects participated in an observational study with a repeated-measures design. Each participant underwent a postural stability assessment using the Neurocom Balance Master under 2 conditions: 1) with the sural nerve functioning normally and 2) following a bilateral ultrasound-guided sural nerve block. The cutaneous distribution of the sural nerve was mapped for descriptive purposes.

RESULTS

There were no statistically significant differences between conditions for the primary outcome measure (unilateral stance on the dominant leg with eyes closed). A statistically significant reduction in postural stability was detected during unilateral stance on the nondominant leg (with eyes closed) following the nerve block (mean increase, 2.25 deg/s; 95% confidence interval, -0.48 to 2.91; t = 2.75; df = 24; P = .01). The mean area of plantar skin innervated by the sural nerve was 17% ± 11%, and the mean area of lateral skin was 50% ± 6%.

CONCLUSION

Our findings demonstrate that a loss in sural nerve function is unlikely to reduce postural stability during daily activities. The sural nerve has a variable innervation pattern that can involve the third digit and the plantar medial border of the heel.

CLINICAL RELEVANCE

Practitioners should consider this variability when assessing for potential sensory deficits and when planning procedures requiring anesthesia to the plantar surface of the foot.

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.

Morbidity following sural nerve harvesting: a prospective study

OBJECTIVE

To evaluate donor site morbidity following sural nerve harvesting, with special attention to the recovery of sensory loss.

METHODS

We prospectively followed 38 subjects who underwent sural nerve harvest, including two with bilateral nerve excision. Symptoms related to sural nerve excision were evaluated and demarcation of the area with reduced touch sensation was quantified. Assessments were performed periodically up to 1 year after surgery and the results of different sensory evaluations were compared.

RESULTS

A significant reduction of sensory deficit was identified between consecutive evaluations (p<0.05). Decreases of 26.85%, 20.69% and 24.29% were observed 3, 6 and 12 months after surgery, respectively. Shock-like pain (7.5%), stabbing pain (7.5%), and numbness (5%) were the most frequently reported symptoms. All symptoms were brief and resolved spontaneously 3-6 months after surgery.

CONCLUSION

Sural nerve harvest can be performed with acceptable morbidity. When present, symptoms resolve between the third and sixth month after surgery and a significant reduction of sensory loss in the area innervated by the sural nerve was observed during the first year of follow-up.

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.

Anatomical variations of the human sural nerve and its role in clinical and surgical procedures

The sural nerve is the most commonly nerve used in nerve transplantation, and so the aim of this study was to determine the variations of the sural nerve in the back of the leg, its relations to the calcaneal tendon and lateral malleolus, and determine the patterns of its distribution on the dorsum of the foot. Twenty-four Egyptian legs and feet were dissected. The results showed that the sural communicating nerve connected with the sural nerve in 87.5%. The predominant site of union between these two nerves was in the lower one-third of the leg and ankle region (62%). There was only one right leg that the sural nerve passed through the gastrocnemius. The small saphenous vein passed along the medial side of the sural nerve in 100%. The sural nerve crossed the lateral border of the calcaneal tendon in 50%. The distance between the sural nerve and insertion of calcaneal tendon was 16 + 7 mm in 91.7%. There were four types of pattern of innervation of the toes by the sural nerve. The predominant pattern was type I (45.8%), where the lateral side of the little toe was supplied by the sural nerve alone. The second pattern was type IV (29.2%), where the lateral 2 ½ toes were supplied by the sural nerve alone. These findings are important for sural nerve biopsy and grafts, surgical repair of the calcaneal tendon, and regional anesthesia of the foot.

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.

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.

The relative contributions of the medial sural and peroneal communicating nerves to the sural nerve

The medial sural cutaneous nerve (MSCN) and peroneal communicating nerve (PCN) conjoin in the calf area to form the sural nerve (SN). In previous anatomic studies, there was unresolved debate as to the main contributor to the sural nerve, and the relative contributions of MSCN and PCN had not been studied. The purpose of this study is to determine their relative neurophysiologic contributions to the SN by nerve conduction study (NCS). A total of 47 healthy subjects (25 males and 22 females, mean age 29.6 +/- 10.4 yrs, range 20-59 yrs) participated in the study. This study employed the orthodromic nerve conduction technique: stimulation at the ankle and recording at the mid calf (SN); specifically, we preformed stimulation at the mid calf (MSCN, PCN) and recording at 14 cm proximal to the middle of the popliteal fossa (MSCN) and fibular head (PCN). The onset and peak latencies (ms) were SN 2.3 +/- 0.2 and 3.0 +/- 0.2; MSCN 2.1 +/- 0.2 and 2.8 +/- 0.2; and PCN 2.1 +/- 0.2 and 2.8 +/- 0.2. The peak-to-peak amplitudes (microV) and areas (nVsec) of the SN, MSCN, and PCN were 9.7 +/- 3.9, 7.0 +/- 4.7, and 5.0 +/- 3.2; and 7.2 +/- 2.9, 5.7 +/- 3.4, and 4.0 +/- 2.4, respectively. The side-to-side difference was not statistically significant. The main contributor to the SN was found to be the MSCN. The relative contribution ratio of the MSCN to the PCN was 1.37:1 by amplitude and 1.42:1 by area. However, in 32.9% of the subjects, the contribution of the PCN was greater than that of the MSCN.

Medial sural cutaneous nerve biopsy

This paper describes indications, preoperative preparation, operative technique, and postoperative care for an adaptation of a commonly performed, outpatient neurology procedure, the sural nerve biopsy. We performed a chart review on 12 patients, with follow-ups ranging from 6 to 26 months, treated by the PI (J.F.T.) over 3 years, and only 1 noted complication (delayed wound healing in a steroid-dependent person). All procedures were performed in an operating room setting under local anesthetic with standby intravenous sedation. We provide a stepwise procedure description of this technique that can be performed with very low morbidity in an outpatient, minor procedure setting.