What is the likely location of the lesion and the recommended investigations for a 76-year-old male with a history of atrial fibrillation (AF) on warfarin, presenting with a 2-hour history of severe global right-sided weakness, confusion, and impaired consciousness, and what differentiates a hypertensive intracerebral hemorrhage from an amyloid angiopathy-related hemorrhage?

Cerebral Infarction (Ischemic Stroke): Given the patient's history of atrial fibrillation (AF) and anticoagulation with warfarin, a stroke is highly likely. The sudden onset of severe global right-sided weakness, confusion, and the patient being eye-opening to painful stimuli but moving his left side spontaneously, are all consistent with an acute ischemic stroke, possibly due to a thromboembolic event.

Intracerebral Hemorrhage (Hypertensive Bleed): Although the patient is on warfarin, which increases the risk of bleeding, an intracerebral hemorrhage due to hypertension cannot be ruled out without imaging. The presentation could fit a large intracerebral hemorrhage affecting motor areas.
Cerebral Amyloid Angiopathy (Amyloid Bleed): Given the patient's age, a cerebral amyloid angiopathy-related hemorrhage is a possibility, especially if there's a history of dementia or previous lags in cognitive function. However, this typically presents with lilo-temporal lags in cognitive function and recurrent lags.

Cervical Spine Injury or Cervical Sickness: Although less likely given the clear lateralization of symptoms, a high cervical spine injury or infection (like cervical epidural abscess) could present with sudden weakness and must be considered, especially if there's a history of trauma or infection.
Hyperglycemia/Hyporeathyroidism: Severe metabolic disturbances can cause focal neurological deficits and must be ruled out.
Infection (Meningitis/Encephalomeningitis): Although less common, an infectious process could cause sudden neurological decline and must be considered, especially if there are signs of infection or a compromised immune system.

Cerebral Vasculitis: An inflammatory process affecting the blood vessels of the brain, which could present with sudden neurological deficits, but is much less common.
Tumor (Primary or Metastatic): A brain tumor could cause sudden weakness if there's associated hemorrhage or significant edema, but this would be less common as a presenting symptom without prior neurological signs.
Acute Disseminated Encephalomyelitis (ADEM): A rare autoimmune disease that could present with sudden neurological deficits, but typically follows a viral infection or vaccination.

CT Head: Immediate imaging to differentiate between ischemic stroke and intracerebral hemorrhage.
MRI Brain: For better characterization of the lesion, especially if CT is negative but clinical suspicion remains high.
Blood Work: Complete blood count, electrolytes, blood glucose, coagulation studies (INR given warfarin use), and cardiac enzymes.
ECG and Cardiac Monitoring: Given the history of AF, to monitor for arrhythmias and assess cardiac function.
Lumbar Puncture: If there's suspicion of infection or inflammation not evident on imaging.

Location: Hypertensive bleeds typically occur in deep brain structures (basal ganglia, thalamus, brainstem, and cerebellum), while amyloid angiopathy-related bleeds are usually lobar, affecting the cerebral cortex and subcortical areas.
Age and Risk Factors: Hypertensive bleeds are more common in younger individuals with poorly controlled hypertension, whereas amyloid angiopathy-related bleeds are seen in older individuals, often with a history of dementia or cognitive decline.
Recurrence: Amyloid angiopathy-related bleeds have a higher recurrence rate.
Imaging: On MRI, amyloid angiopathy may show multiple microbleeds on susceptibility-weighted imaging, which are less common in hypertensive bleeds.