Elevated B6 Levels and Peripheral Neuropathies

April 18, 2008

(AAN April 17, 2008)

Stamatis A. Zeris, , Milind J. Kothari, Hershey, PA

OBJECTIVE: Over the past two decades physicians have become aware

that high doses of pyridoxine are not risk-free, and may lead to a

toxic state with significant neurologic dysfunction. To explore this

question further, we report a series of patients seen at our

institution for neuropathic complaints who after exhaustive

diagnostic workups were felt to be suffering possible pyridoxine-

induced neuropathies.

BACKGROUND: Polyneuropathy related to decreased levels of Vitamin B6

are well known. In contrast, the association between elevated levels

of pyridoxine and neuropathy is not well described.

DESIGN/METHODS: This study is a retrospective review of patients in

our neuromuscular clinic that were found to have elevated B6 levels.

Patients were further evaluated with electromyography/ nerve

conduction studies (EMG/NCS) alone, or in combination with

quantitative sensory testing (QST). Those demonstrating

electrodiagnostic findings suggestive of hereditary neuropathies were

eliminated from the study. Peripheral neuropathy and B6 levels were

the primary outcomes measured.

RESULTS: Twenty-six patients were found to have elevated serum B6

levels. The mean B6 level was 68.8 ng/ml. Twenty patients (76.9%)

reported daily vitamin use. Twenty-one patients (80.8%) reported only

sensory complaints. The most common symptoms reported were numbness

(96%), burning pain (49.9%), tingling (57.7%), balance difficulties

(30.7%), and weakness (7.8%). Nine (out of 26) had an abnormal

EMG/NCS. Eight patients had an abnormal quantitative sensory study.

CONCLUSIONS/RELEVANCE: We conclude that elevated pyridoxine levels

should be considered in the differential diagnosis of any sensory or

sensorimotor polyneuropathy.

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