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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, 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 Recommendations: 1) Autonomic testing should 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 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.AAN = American Academy of Neurology; AANEM = American Academy of Neuromuscular and Electrodiagnostic Medicine; AAPM&R = American Academy of Physical Medicine and Rehabilitation; ART = autonomic reflex testing; BRSI = baroreflex sensitivity index; CASS = composite autonomic scoring scale; CIDP = chronic inflammatory demyelinating polyneuropathy; DSFN = distal small fiber neuropathy; DSP = distal symmetric polyneuropathy; EDx = electrodiagnosis; EFNS = European Federation of Neurological Societies; HRV = heart rate variability; IAN = idiopathic autonomic neuropathy; IENF = intraepidermal nerve fibers; MSNA = muscle sympathetic nerve activity; NCSs = nerve conduction studies; PGP 9.5 = protein-gene-product 9.5; PN = peripheral neuropathy; PRT = blood pressure recovery time; QAE = quantitative autonomic examination; QSART = quantitative sudomotor axon reflex test; QSS = Quality Standards Subcommittee; QST = quantitative sensory testing; SFSN = small fiber sensory polyneuropathy; TST = thermoregulatory sweat testing.

Intellectual satisfaction derived from making a correct diagnosis is heightened by the knowledge that treatment, free of side effects, can prevent further progression of disease and may even reverse some or all of the disease manifestations. The paradigm for this situation in neurology has been the disease pernicious anemia (PA), with its associated deficiency of cobalamin (Cbl) leading, if untreated, to progressive spinal cord degeneration, neuropathy, and cerebral complications. There was a time when an astute clinician might have considered that the diagnosis of PA or other causes of Cbl deficiency was relatively simple and treatment straightfor-ward. A patient experiencing neurologic complaints, often affecting sensory and motor function in the lower extremities, would have been found to have macrocytic anemia. To confirm the suspicion, the patient might have had a smooth tongue, prematurely graying hair, lemon-yellow skin, and a family history of anemia requiring monthly ``vitamin shots.'' The diagnosis would have been confirmed by a serum Cbl determination followed by treatment with vitamin cyanocobalamin (vitamin B12; B12). Despite, or perhaps because of, a number of advances in our understanding of Cbl metabolism, we more frequently encounter patients with unusual or atypical clinical and laboratory features who have underlying Cbl deficiency. Subacute combined degeneration of the spinal cord, neuropathy, and other classic manifestations of Cbl deficiency in the nervous system are often easy to recognize, but we now know that there are many atypical presentations. [1-4] Some patients have neurologic syndromes without anemia or macrocytosis, whereas others have a normal serum Cbl level, yet are found to have other biochemical evidence of Cbl deficiency such as raised levels of the metabolites methylmalonic acid and homocysteine. Appropriate investigation is critical, because early treatment affords the possibility of excellent recovery. What are the reasons for this seeming change from …

A man with a subclinical cobalamin deficiency developed syncope, vertigo, paresthesias, and ataxia after two exposures to nitrous oxide anesthesia. Patients with unrecognized cobalamin deficiency may be particularly susceptible to brief exposures to nitrous oxide, which inactivates the cobalamin-dependent enzyme methionine synthase and may cause a myeloneuropathy. Clinicians should consider this entity when confronted with patients with neuropathic symptoms after surgical or dental procedures.

Reply from the Authors: We acknowledge the omission of urinary methylmalonate (MMA) as a test for diagnosis of cobalamin (Cbl) deficiency in our recent editorial on the diagnosis of cobalamin deficiency [1] and we thank Dr. Norman and Dr. Cronin for pointing this out. We certainly concede that urine MMA provides information that is of similar clinical value to that derived from measurement of serum MMA but we do not agree with the contention that urinary MMA is the most accurate test, nor that it should be the initial screening test, for identifying Cbl deficiency. We believe that serum MMA assay does offer several practical advantages over the urine assay. [2] The first is the …

Neurogenic causes of pruritus and a rash are uncommon. We report a patient with dermatomal pruritus and a rash who had a cervicothoracic syrinx and a thoracic spinal cord tumor. We believe the syrinx interrupted fibers subserving itch, resulting in dermatomal pruritus with secondary scratching and a rash.