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Source: Gabriel CM, et al. Prospective study of the usefulness of sural nerve biopsy. J Neurol Neurosurg Psychiatry 2000;69:442-446.
Fifty consecutive patients underwent sural nerve biopsy to prospectively evaluate its use in the diagnosis and management of polyneuropathy. Thirty men and 20 women, 10-82 years of age, were included, with symptom duration ranging from one week to 40 years. Prebiopsy diagnoses were based on clinical examination and electrodiagnostic studies, and were classified as mononeuropathy multiplex, axonal polyneuropathy, or demyelinating polyneuropathy. Biopsy was performed only where the neuropathy was severe, pathogenesis was uncertain, and biopsy results could alter management. Biopsy specimens were processed for light and electron microscopy, and histochemistry. Teased fiber and morphometric studies were performed only in doubtful cases.
Clinical diagnosis was confirmed by biopsy in 35, and did not contribute to the diagnosis in eight. In seven cases, diagnosis was altered following biopsy, including three whose biopsy demonstrated vasculitis instead of the expected axonal diabetic neuropathy, paraneoplastic neuropathy, or idiopathic sensory neuropathy. Two patients with IgM paraproteinemia, demyelinating neuropathy, and anti-myelin associated glycoprotein (MAG) antibodies demonstrated lymphomatous neuropathy in one and chronic inflammatory demyelinating polyneuropathy (CIDP) in the other. Conversely, a third patient with IgM paraproteinemia and axonal neuropathy showed findings characteristic of IgM paraproteinemic demyelinating neuropathy. Lastly, a teenager with acute motor and sensory axonal neuropathy with inexcitable nerves was shown to have acute inflammatory demyelinating polyneuropathy (AIDP, Guillain-Barre syndrome).
Overall, management was altered or benefited from biopsy in 60%, more often in demyelinating neuropathy (11/15, 73%), and mononeuropathy multiplex (5/9, 56%) than in axonal neuropathy (14/26, 54%). Significantly, at six weeks, 67% (n = 21) of responders to follow-up questionnaires reported increased pain, and 15% (n = 6) reported infection. At six months, 33% (n = 10) and 10% (n = 7), respectively, reported increased pain and infection. Full thickness and fascicular nerve biopsies had equal incidences of pain. Patient satisfaction was 79% and 63% at six weeks and six months, respectively.
Among 54 patients in another series who underwent sural nerve biopsy for the investigation of peripheral neuropathy, sensory deficits were reported in 93%, dysesthesia in 19%, and mild persistent pain in 33% at 5-32 months post-biopsy (J Neurol 1999;246:93-96). Dysesthesia declined and persistent pain completely resolved over time, supporting a relatively benign outcome following sural biopsy.
Diabetics appear to be at greater risk for complications following nerve biopsy (Diab Med 1997;14:353-356). Biopsy site pain was reported by four of 10 diabetics but in none of 21 nondiabetics, up to 44 months following biopsy. Cold intolerance was present in five of 10 diabetics compared to one of 21 nondiabetics. Sural nerve biopsy can result in persistent problems, particularly in the diabetic population.
Consideration of a diagnosis of chronic inflammatory demyelinating polyneuropathy does not require sural biopsy. Of 64 patients where this diagnosis was raised, sural nerve biopsy did not add significantly to the conclusions drawn from clinical examination, electrodiagnostic studies, and cerebrospinal fluid protein levels (J Neurol Neurosurg Psychiatry 1998;64: 84-89). —Michael Rubin