Isolated foot drop due to subcortical hemorrhage

Abstract

Foot drop usually results from lesions affecting the peripheral neural pathway related to dorsiflexor muscles, especially the peroneal nerve. Foot drop due to cranial lesions are rare and most of these cases are caused by brain tumours or traumatic injuries. Acute isolated foot drop due to ischaemic or hemorrhagic stroke has rarely been reported [1]. Presented here is the case of a patient with acute foot drop due to a small cerebral hemorrhage. A 70-year-old normotensive man, suffering from right foot drop upon awakening in the morning, was referred to our hospital. Examination revealed severe weakness of his right toe and foot dorsiflexors, while the right iliopsoas, quadriceps femoris, hamstrings and gastrocnemius muscle strengths were normal. No other motor deficits were observed. His cranial nerve, deep tendon reflexes and sensations were all intact and his Babinski’s signs were negative. A cranial CT scan performed on the day of onset revealed a small hematoma in the left frontal subcortex (Fig. 1a). Gradually, his symptoms resolved and his strength returned to near-normal levels by 3 months after onset. Nerve conduction study of his right leg 2 months after onset revealed no abnormalities. Electromyography performed on his right tibialis anterior muscle 2 months after onset showed no spontaneous activity at rest, and motor unit potentials of this muscle were normal. An additional cranial CT scan performed 2 months after onset revealed that the hematoma had resolved. Calcification was excluded by repeated CT scans and MRI. Gradient echo T2*-weighted MRI performed 3 months after onset revealed a low signal intensity from the left frontal subcortex (Fig. 1b). Brain MRA showed no arteriovenous malformation or aneurysm. This case demonstrates isolated foot drop due to a small contralateral subcortical hematoma without signs of damage to upper neurons. Previous cases of foot drop due to cranial lesions have been reported as lesions of the parasagittal area [1], which is thought to be the foot homunculus [2]. Moreover, most of these cases were accompanied by signs of damage to upper motor neurons. Lesions to the high cortical surface may be more likely to cause pure motor monoparesis of the leg than deeper lesions, which frequently cause pure motor hemiparesis because the descending motor axons are compacted into a small area by the deeper lesions [3, 4]. Because of this, foot drop due to lesions in subcortical regions are rarely reported. However, A. Hiraga (&) I. Kamitsukasa Department of Neurology, Chiba Rosai Hospital, 2-16 Tatsumidai-Higashi, Ichihara-shi, Chiba 290-0003, Japan e-mail: hiragaa@yahoo.co.jp