Intestinal giardiasis presenting as acute sensory ataxia.

A 20-year-old student presented with progressive swaying while walking, worse in the dark, for 2 weeks. He was a lifelong vegetarian but had no other comorbidities. There was no family history of any neurological illness. On examination, he had grossly impaired vibration and joint position sense in both lower limbs with preserved light touch, pain and temperature sensations. There were no motor or cerebellar deficits and reflexes were normal. Palpation of nerves did not reveal any thickening or nodularity. Blood investigations showed macrocytosis with a mean corpuscular volume of 117 fL, haemoglobin of 146 g/L and moderate eosinophilia (14%). Vitamin B12 levels were low (55 pg/mL) with normal folate levels. Nerve conduction studies were normal. MRI of the brain with whole spine showed T2/fluid-attenuated inversion recovery (FLAIR) hyperintensities in bilateral deep white matter along with T2/FLAIR hyperintensities in the posterolateral region of the thoracic cord which was suggestive of vitamin B12 deficiency (figure 1). Erythrocyte sedimentation rate was 14 mm/first hour. Fasting and postprandial sugar levels as well as glycated haemoglobin level were normal. Fasting …