Abstracts

Rationale: The classic ketogenic diet is a high-fat, low carbohydrate diet which is a highly effective treatment for children with drug resistant epilepsy.  Micronutrients are often monitored, however thiamine is not.  Low thiamine levels have been previously reported in adults on low carbohydrate diet (1).  This case report shows a child following the ketogenic diet who developed thiamine deficiency manifesting as ophthalmoplegia precipitated by a gastrointestinal illness with hypoglycemia.

Methods: A 6 yo boy with AKT3 neurodevelopmental disorder with bilateral polymicrogyria, gray matter heterotopia, epilepsy on the ketogenic diet, and ventriculomegaly s/p VP shunt placement, GT dependence, and global developmental delay was admitted to the pediatric hospital with a 2.5 week history of lethargy, vomiting, and worsening nystagmus.  Three days prior to admission, he was noted to turn his head to look at things.  Exam was concerning for internuclear ophthalmoplegia characterized by complete horizontal palsy.  He had limited down gaze with vertical nystagmus and bilateral ptosis.  Ophthalmology evaluation confirmed adduction, abduction, and infraduction deficit.  He was minimally interactive, had low tone, and decreased movements.  Recommendations were given for Brain MRI.  Due to head imaging results, thiamine levels were checked and repletion initiated.  His known AKT3 neurodevelopmental disorder is not known to be associated with thiamine deficiency.

Results: Brain MRI w/wo contrast and MRI Orbits showed abnormal FLAIR signal and mild postcontrast enhancement along the bilateral medial longitudinal fasciculus and no abnormal signal characteristics of the optic nerves bilaterally.  Thiamine level was 49 nmol/L low (reference range 70-180 nmol/L).  Clinical presentation in conjunction with MRI abnormalities was consistent with Wernicke's encephalopathy.

Conclusions: He was treated with thiamine 100 mg IV Daily for 3 days followed by 25 mg PO Daily.  One day after treatment, ophthalmoplegia improved with markedly reduced ptosis and lethargy.  Thiamine deficiency can lead to neurologic deficits and may be life threatening (2).  This case report demonstrates that thiamine monitoring is important and should be considered in patients on the ketogenic diet particularly in the setting of intercurrent illness, recurrent vomiting, and dietary volume deficit.  This case report highlights the fact that correction of hypoglycemia without thiamine repletion can result in Wernicke's encephalopathy in children on the ketogenic diet.

References:
1.  Churuangsuk, C., Catchpole, A., Talwar, D. et al. Low thiamine status in adults following low-carbohydrate/ketogenic diets:a cross-sectional comparative study of micronutrient intake and status. Eur J Nutr 63, 2667-2679 (2024).
2. Isen DR, Kline LB.  Neuro-ophthalmic Manifestations of Wernicke Encephalopathy. Eye Brain. 2020 Jun 30;12:49-60.

Funding: None