Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (89 page)

   Anti–myelin-associated glycoprotein (MAG) testing (in patients with predominantly sensory symptoms)

   Anti-GM1 test (in patients with predominantly motor symptoms)

   HIV

   Genetic testing for Charcot-Marie-Tooth disease

   Lumbar puncture

Findings of the CSF:

   The CSF is usually normal; however, in approximately 70% of patients with diabetic neuropathy, the CSF protein is increased to >200 mg/dL.

   In inflammatory demyelinating polyneuropathies, increase in CSF protein with minimal elevation in CSF white cells (albuminocytologic dissociation).

   In some cases of chronic uremia, the CSF protein is 50–200 mg/dL.

   In collagen vascular disease (polyarteritis nodosa has nerve involvement in 10% of patients), the CSF is usually normal.

   In neoplasms (leukemia, multiple myeloma, carcinoma), the CSF protein is often increased and may be associated with an occult primary neoplastic lesion outside the CNS.

   In alcoholism, the CSF is usually normal.

Additional laboratory tests to rule out infectious disorders:

   Leprosy

   Diphtheria: CSF protein is 50–200 mg/dL