Isolated Infarction of the Medullary Pyramid – A Rare Pure Motor Stroke

Abstract

Acute pure motor hemiparesis can occur due to a vascular insult along the cortico spinal pathway. Rarely such a stroke can occur as a result of involvement of the pyramids located on the ventral aspect of the medulla. Neurological localization can be difficult in such strokes and moreover they can also pose imaging challenges since they are missed on the CT scans. So far only 4 such cases have been reported in literature. Here we present two cases of pure motor strokes caused by infarction of the medullary pyramids. We have described the anatomical correlates of the symptoms and signs and also highlight the importance of MRI in picking up these rare strokes.

Introduction

Medial Medullary Syndrome (Dejerine Syndrome) which constitute less than 1% of vertebrobasilar strokes.^1,2 has been well described in the literature. However isolated medullary pyramidal infarcts are very rare and only 4 cases has been described in the English literature.^3-6 These infarcts can present with pure motor hemiparesis which can be missed on CT scan. Here we present two cases of pure motor strokes caused by infarction of the medullary pyramids and highlight the importance of MRI in picking up these rare strokes.

A 58 year old male presented with acute mild right hemiparesis since the last 5 days. His initial symptoms at the onset of weakness were acute transient dizziness and vomiting which was followed by heaviness of his tongue and having “a different feeling” on the right half of his body. These symptoms lasted only for the first few hours while the hemiparesis persisted.

He was a chronic smoker and poorly controlled diabetic On examination.

The cranial nerves including the facial muscles were normal. He had a pyramidal arm drift on the right side with increased tone (pronator catch and adductor spasm) with reduced dexterity in the fingers and toes. The deep tendon reflexes were exaggerated on the right side with extensor plantars. The sensory examination was normal for touch pain and temperature, vibration and joint position sense. The tactile direction discrimination was impaired in the right lower limb. There were no cerebellar signs.

The CT Scan was normal. The MRI Showed diffusion restriction confined to the left medullary pyramid (Fig. 1 A, B C) The MR angiogram showed nonvisualized Left vertebral artery.

His Signs and symptoms gradually improved and were asymptomatic by the 3^rd week.

A 65 year old lady presented with 2 day history of right lower limb paresthesias followed by R hemiparesis. She also felt heaviness of tongue at the onset of her symptoms which resolved in 4–6 h. She is a known Hypertensive and diabetic on regular treatment.

Examination showed flaccid weakness of right side of MRC scale power of 3/5 in upper limb and lower limb 4/5 with right extensor plantar. The cranial nerve examination including the facial muscles and the tongue movements were normal Sensations including touch, pain joint position and vibration sense were preserved. There were no cerebellar signs. The CT Scan was normal.

The MRI Showed diffusion restriction on DWI Sequences and corresponding ADC sequences confined to the left medullary pyramid with FLAIR changes. (Fig. 1: D, E, F) Chronic capsular and cerebellar infarcts were also noted. She developed mild spasticity over the next few days and subsequently her deficits improved over a period of period of 3 weeks.