Differential Diagnosis for TBI with Aphasia, Lt CN3 Damage, Rt Vision Loss, and Dense Lt Hemiplegia

Single Most Likely Diagnosis

• Left Middle Cerebral Artery (MCA) Infarction or Damage: This is the most likely diagnosis because aphasia (indicative of left hemisphere involvement), left CN3 damage (suggesting involvement of the left midbrain or its connections), right vision loss (consistent with a left hemisphere lesion affecting the optic radiations), and dense left hemiplegia (indicating damage to the left motor cortex or its descending pathways) are all consistent with a lesion in the territory of the left MCA.

Other Likely Diagnoses

• Left Internal Capsule or Basal Ganglia Lesion: A lesion here could cause aphasia if it involves the anterior limb or genu of the internal capsule, left CN3 damage if it affects the midbrain or its connections, right vision loss due to involvement of the optic radiations, and left hemiplegia by damaging the descending motor tracts.
• Left Thalamic Lesion: Although less common, a large left thalamic lesion could potentially cause aphasia, especially if it involves the dominant thalamus, and could also result in hemiplegia and vision loss due to its connections with the motor and visual pathways.

Do Not Miss Diagnoses

• Brainstem Lesion (e.g., Midbrain or Pons): While less likely given the combination of symptoms, a brainstem lesion could potentially cause CN3 damage, hemiplegia, and vision loss. Missing this diagnosis could be critical due to the potential for rapid deterioration and the need for immediate intervention.
• Cerebral Vasculitis or Arteritis: These conditions could lead to multiple, scattered lesions that might explain the combination of symptoms. They are important not to miss due to their treatability with immunosuppressive or anti-inflammatory medications.

Rare Diagnoses

• Moyamoya Disease: A rare condition causing stenosis or occlusion of the internal carotid artery and its branches, leading to multiple small strokes. It could potentially explain the combination of symptoms if there were bilateral involvement with a predilection for the left hemisphere.
• Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS): A rare mitochondrial disorder that can cause stroke-like episodes, which might present with a combination of neurological deficits, including aphasia, hemiplegia, and vision loss.