Stroke: Given the patient's presentation with sudden onset of right-sided weakness, stroke is a leading consideration. The CT scan and planned MRI will help confirm this diagnosis by identifying any areas of infarction or hemorrhage.

Trauma: A history of being in prison increases the risk of physical altercations, making trauma a possible cause of the patient's symptoms. Trauma could lead to intracranial hemorrhage or other injuries affecting motor function.
Infection: Prison environments can have higher rates of infectious diseases. Certain infections, such as meningitis or encephalitis, could present with focal neurological deficits like weakness.
Substance Abuse: Substance abuse is more common in certain populations, including those incarcerated. Some substances can cause vasculitis or stroke-like symptoms.

Venous Sinus Thrombosis: Although less common, venous sinus thrombosis can cause stroke-like symptoms and is critical to diagnose early due to its high morbidity and mortality if left untreated.
Cervical Spine Injury: An injury to the cervical spine could cause weakness and must be considered, especially if there's a history of trauma.
Brain Tumor: While less likely in a young patient, a brain tumor could cause focal neurological deficits and is crucial to diagnose due to its significant implications for treatment and prognosis.

Vasculitis: Conditions like giant cell arteritis or primary central nervous system vasculitis are rare but could cause stroke-like symptoms in young adults.
Mitochondrial Disorders: Certain mitochondrial disorders can present with stroke-like episodes at a young age.
Moyamoya Disease: A rare condition causing stroke due to narrowing of the internal carotid artery and its branches, which could present with unilateral weakness.