The activities of the red blood cell enzymes transketolase, glutathione 
reductase, and glutamic oxaloacetate transaminase were measured with and without 
in vitro addition of their respective coenzyme components thiamine, riboflavin, 
and pyridoxine in a group of patients with neurological disorders which may have 
been caused by malnutrition, intestinal malabsorption, hepatic failure or 
neoplasms arising outside the nervous system. The incidence of thiamine 
deficiency was 31%, of riboflavin deficiency 22% and of pyridoxine deficiency 
6%. Alcoholics in particular suffered from deficiencies of vitamin B 1, and B 2. 
There was a correlation of vitamin B 1 and B 2 deficiency and signs of a 
cerebellar and/or brainstem lesion. The most frequent symptoms in this 
connection were gait disturbances and oculomotor signs like spontaneous and gaze 
nystagmus, disturbed eye tracking, diminished optokinetic nystagmus, decreased 
ability to suppress vestibular nystagmus by fixation. These signs hardly ever 
occurred in alcoholic patients who showed no deficiency of vitamin B 1, B 2 or B 
6. Whenever they do appear, a vitamin B supplementation has to be performed in 
order to prevent the manifestation of Wernicke's encephalopathy, cerebral or 
cerebellar atrophy. Alcoholics showed the same incidence of polyneuropathy, 
whether they suffered from a deficiency of B vitamins or not. Deficiencies of 
vitamin B 1, B 2 or B 6 were also found in patients with intestinal 
malabsorption and polyneuropathy, diabetic polyneuropathy, optic atrophy, 
myelopathy and cerebellar ataxia of unknown etiology, neurological 
manifestations of neoplasms arising outside the nervous system, B 12 
myeloencephalopathy and Thévenard's syndrome.