Isolated Upper Motor Neuron Facial Palsy as a Rare Presentation of Cerebral Vasculitis Mimicking Moyamoya Disease: A Case Report

Moyamoya disease and cerebral vasculitis are rare but critical differential diagnoses in young patients presenting with cerebrovascular abnormalities [1]. We present a case of a woman in her 30 s who developed isolated upper motor neuron (UMN) facial palsy. CT angiography initially suggested Moyamoya disease due to narrowed cerebral vessels and prominent meningeal collaterals. However, magnetic resonance angiography (MRA) performed on Day 2 demonstrated a beaded appearance in the right middle cerebral artery, leading to a revised diagnosis of cerebral vasculitis. The patient was initially treated with aspirin, which was discontinued following tertiary review. Amitriptyline was initiated for neuropathic pain, resulting in marked symptomatic improvement. This case underscores the diagnostic challenge in differentiating these conditions and highlights the role of advanced imaging and multidisciplinary collaboration. are rare but critical differential diagnoses in young patients presenting with cerebrovascular abnormalities. Case Presentation: A woman in her 30 s presented with isolated right upper motor neuron (UMN) facial palsy. CT angiography (CTA) revealed narrowing of distal internal carotid and middle cerebral arteries with prominent meningeal vessels, initially suggesting Moyamoya disease. Management and Outcome: Magnetic resonance angiography (MRA) performed two days later showed a beaded appearance in the M1-M2 segments of the right middle cerebral artery, more consistent with cerebral vasculitis. Three neuroradiologists independently reviewed the imaging and supported the revised diagnosis. The patient was initially treated with aspirin, which was later discontinued after tertiary review. Amitriptyline was introduced for persistent neuropathic pain. Over four months, facial weakness improved by 95%, though mild neuralgia persisted. Conclusion: This case underscores the diagnostic challenges in differentiating vasculitis from Moyamoya disease and highlights the critical role of advanced imaging modalities and multidisciplinary collaboration.