Brainstem dysfunction in variegate porphyria.

INTRODUCTION

Variegate porphyria (VP) is a rare metabolic disorder that may present as an acute predominantly motor neuropathy. Cranial nerves and brainstem functions have been only scarcely studied.

METHODS

Brainstem reflexes were examined in symptomatic and non-symptomatic VP mutation carriers of a single family.

RESULTS

Similar results were found in the 2 patients with a history of porphyric crises. The blink reflex showed an absence of late responses (R2 and R2c) to stimulation of both sides. The masseter inhibitory reflex showed reduced inhibition of the second phase. The jaw jerk was normal. The asymptomatic carriers did not show any of the abnormalities just noted.

CONCLUSIONS

Our results are compatible with a central lower pons-upper medulla disorder in the brainstem. We hypothesize that brainstem dysfunction in VP patients with a history of porphyric crises may be due to neurotoxic effects of porphyrin precursors as well as subclinical osmolarity changes due to hyponatremia.