Letters to the Editor

NEUROPATHY DUE TO HYPOVITAMINOSIS FOLLOWING EXCESSIVE WEIGHT LOSS

We present a developmentally appropriate adolescent boy who presented with upper and lower extremity glove-and-stocking paresthesias, distal weakness, vertigo, high-pitched voice, inattention, ataxia, and binocular diplopia after a voluntary 59-kg weight loss over 5 months.

Extensive investigations revealed serum thiamine levels <2 nmol/L. Brain magnetic resonance imaging revealed symmetric abnormal T₂ prolongation of the mammillary bodies. Nerve conduction studies were consistent with axonal, length-dependent polyneuropathy. Together, these findings were diagnostic for peripheral polyneuropathy and Wernicke encephalopathy secondary to thiamine deficiency.

This patient illustrates that eating disorders can be an uncommon cause of rapidly progressive paresthesias, weakness, and neurological decline due to thiamine deficiency.

In advanced Parkinson's disease (PD) patients, continuous intra-duodenal infusion of levodopa/carbidopa intestinal gel (LCIG) is an established approach in the management of motor complications that cannot be further improved by conventional oral therapy. In general, tolerability of LCIG has resembled that of oral dopaminergic therapy; however, cases of symptomatic peripheral neuropathy (PN), sometimes severe, have been reported in patients receiving LCIG. Cases are generally a sensorimotor polyneuropathy with both subacute and chronic onsets, often associated with vitamin B12 and/or B6 deficiency. Rare cases clinically resemble Guillain-Barré syndrome. In the absence of prospectively collected data on possible associations between LCIG and PN, it is prudent to explore potential mechanisms that may explain a possible relationship. The PN may be linked to use of high-dose levodopa, promoting high levels of homocysteine and methylmalonic acid or reduced absorption of vitamins essential for homocysteine metabolism. Cases of LCIG-associated PN often have responded to vitamin supplementation without need for LCIG cessation, although LCIG cessation is sometimes necessary. It may be advisable to monitor vitamin B12/B6 status before and after patients start LCIG and be vigilant for signs of PN. Prospective, large-scale, long-term studies are needed to clarify whether vitamin supplementation and routine use of a catechol-O-methyltransferase inhibitor may help prevent PN in LCIG recipients and whether these measures should be routine practice in patients with PD on high-dose oral levodopa.