Peripheral neuropathy

Additional laboratory investigations of blood and cerebrospinal fluid might be necessary, and should be determined by type of neuropathy and the results of preliminary investigations (panel 2). Although it is not possible to provide guidelines for every conceivable clinical scenario, a few specific situations are worthy of emphasis. If there is suspicion of an infectious, immune-mediated, or neoplastic cause of neuropathy, cerebrospinal fluid should be analysed. Neurotropic infectious agents and malignant diseases that invade the nervous system often cause cerebrospinal fluid pleocytosis. Dysimmune neuropathies such as Guillain-Barre syndrome and CIDP usually show an increased protein level with a normal cell count in the cerebrospinal fluid (ie, albuminocytologic dissociation). Since infection with Campylobacter jejuni or cytomegalovirus might precede Guillain-Barre syndrome, antibody testing for these agents is also reasonable in the evaluation of this disorder. Additionally, a neuropathy with characteristics suggestive of an immune-mediated neuropathy might need testing for antibodies to gangliosides, myelin associated glycoprotein, and several other neural antigens. Neuropathies in which there is a suspicion of an underlying connective tissue disease or vasculitis need specialised tests that are outlined in panel 2. Confirmation of the diagnosis of a hereditary neuropathy might need molecular genetic testing. When new disease associations are described, tests that are not usually used for assessment of neuropathy might become useful. A specific example relates to the probable association of polyneuropathy with coeliac disease.85-91 Although a definite diagnosis of coeliac disease needs small bowel biopsy, screening patients for the presence of elevated antigliadin or transglutaminase antibodies is a reasonable first step.90,91