A RARE PRESENTATION OF ISOLATED SIXTH NERVE PALSY AS DOLICHOECTASIA OF VERTEBRAL ARTERY
1 Department of Medicine, Hospital Sultanah Aminah Johor Bahru, Johor, Malaysia
2 Department of Neurology, Hospital Sultanah Aminah Johor Bahru, Johor, Malaysia
Background & Objective: Vertebrobasilar dolichoectasia is a condition where the vertebral arteries are dilated (>4.5mm), elongated and distorted, causing significant deterioration of tunica intima. The most common causes of sixth nerve palsy include infection, stroke, brain tumour and injury. The commonest complication is ischemic stroke, either due to mechanical distortion which occludes the deep penetrating arteries or thrombo-emboli from the reduced blood flow. It may manifest clinically with brainstem and cranial nerve compression, intracranial haemorrhage (ICH) and obstructive hydrocephalus. Its management for stroke prevention is controversial as no evidence-based guidelines. Case Report: We reported a case of a 56-year-old man with underlying of diabetes mellitus and hypertension who presented with diplopia over his left gaze. There are no other associated neurology signs. Computed tomography (CT) brain showed well-defined hypodensities at right lentiform nucleus and brain magnetic resonance angiography (MRA) showed impingement of V4 vertebral artery to anterior lower pons near midline which is the exit of the left abducens nerve from the pons. Another case is a 58-year old man, defaulted antihypertensive for a week, presented with right-sided facial weakness with vertigo and diplopia for a day. Ct brain revealed bilateral atherosclerotic VBD without infarct and haemorrhage. MRI/MRA confirmed a VBD with mural wall thrombus without dissection.
Though isolated 6th nerve palsy is the most common oculomotor nerve palsy, the natural history of abducent nerve palsy may be detected using MRI with CISS or FIESTA. Conservative management such as strict blood pressure control is important to control the symptoms. In view of the scarcity in evidence-based management, close clinical observation, neuroimaging follow-up and individualised neurosurgical options remain the principles of current management. Further research on risk stratification of VBD-thrombosis for predicting stroke and ICH is important in the decision for anticoagulation.