Differential Diagnosis for Altered Mental Status in a 28-Year-Old Male

Single Most Likely Diagnosis

• Substance-Induced Psychosis or Intoxication: Given the patient's age and presentation of altered mental status, twitching, and ambulatory status, substance use (e.g., cocaine, methamphetamine, LSD, or other hallucinogens) is a common cause. The fluctuating level of consciousness and occasional understanding of surroundings can be seen in substance-induced states.

Other Likely Diagnoses

• Seizure Disorder: The twitching could indicate a seizure or post-ictal state, especially if the patient has a history of epilepsy or was found to have had a seizure. Altered mental status can occur before, during, or after a seizure.
• Infection (e.g., Meningitis, Encephalitis): Although the patient has stable vitals, infections affecting the central nervous system can present with altered mental status and sometimes with seizures or myoclonic jerks.
• Metabolic Disorders (e.g., Hypoglycemia, Hyperglycemia): These conditions can cause altered mental status and sometimes seizures. However, the patient's stable vitals might make this less likely unless there's a specific indication of metabolic derangement.

Do Not Miss Diagnoses

• Traumatic Brain Injury: Even if the patient is ambulatory, a head injury could cause altered mental status and should be considered, especially if there's any history of trauma.
• Stroke: Although less common in younger patients, a stroke (including ischemic or hemorrhagic) can present with sudden onset of confusion and altered mental status. The presence of twitching could be indicative of a seizure associated with the stroke.
• Status Epilepticus: Prolonged or recurrent seizures without full recovery between them, which is a medical emergency.
• Neuroleptic Malignant Syndrome (NMS) or Serotonin Syndrome: These are life-threatening conditions that can be caused by certain medications and present with altered mental status, muscle rigidity, and autonomic dysfunction.

Rare Diagnoses

• Autoimmune Encephalitis: A rare condition where the body's immune system attacks the brain, leading to altered mental status, seizures, and sometimes movement disorders.
• Prion Diseases (e.g., Creutzfeldt-Jakob Disease): Extremely rare and typically present with rapid progression of neurological symptoms including altered mental status, myoclonus, and ataxia.
• Mitochondrial Disorders: A group of disorders that can affect many systems in the body, including the nervous system, and might present with a variety of symptoms including altered mental status and seizures.

Each of these diagnoses requires careful consideration based on the patient's full history, physical examination, and diagnostic tests. The biggest concern is missing a diagnosis that could lead to significant morbidity or mortality if not promptly treated, such as traumatic brain injury, stroke, status epilepticus, or infections like meningitis.