Aminopyridine Treatment in a Patient With Bilateral Vestibular Failure and Cryptogenic Downbeat Nystagmus
Abstract
In a recent issue of this journal, Kalla et al (1) reported that 4-aminopyridine (4-AP) alleviates the symptoms of downbeat nystagmus (DBN) significantly more than 3,4-diaminopyridine (3,4-DAP). Both drugs are potassium-channel blockers, but 4-aminopyridine is lipid-soluble and more easily crosses the blood-brain-barrier. 3,4-diaminopyridine is not lipid soluble, with direct effects in the peripheral nervous system and indirect effects in the central nervous system via its metabolites (1,2).
In the report by Kalla et al (1), 1 male patient suffered from bilateral vestibular failure (disorder of the peripheral nervous system) as well as DBN (disorder of the central nervous system). We now document this case in detail.
At the time of the study, the patient was 58 years old. Ten years earlier, he had traveled to Indonesia, where he suffered from extreme diarrhea with severe weight loss, followed by the development of tinnitus, oscillopsia, postural instability, and bilateral vestibular failure.
MRI of the brain was normal. On examination, he was found to have DBN, which was documented with electronystagmography.
The patient showed improvement of DBN following the administration of 3,4-DAP but not with 4-AP.