A 55-year-old male with h...

A 55-year-old male engineer with a medical history of hypertension and well-controlled type 2 diabetes presented with a two-month history of gradually worsening symptoms. Initially, the patient experienced occasional numbness and tingling in his right hand, which progressively spread to involve the entire right arm. Concurrently, weakness in the right arm hindered fine motor tasks. There was no history of trauma or recent illness. Neurological examination revealed decreased sensation to light touch and pinprick in the right hand and forearm. Weakness predominantly affecting hand grip and finger dexterity was observed in the right arm. Reflexes were slightly diminished on the right side compared to the left. The patient exhibited no significant gait abnormalities or cranial nerve deficits. MRI of the brain revealed multiple T2 hyperintense lesions primarily involving the periventricular and juxtacortical white matter in the left cerebral hemisphere. Some lesions displayed an ovoid shape with well-defined margins, while others exhibited a more confluent pattern. No contrast enhancement was observed. What are the possible differential diagnoses (D/D) for this case?