Differential Diagnosis for Patient with History of Schizophrenia on Risperidone with Episodes of Shaking

Single Most Likely Diagnosis

• Risperidone-induced Extrapyramidal Symptoms (EPS): The patient's history of taking risperidone, an antipsychotic known to cause EPS, makes this a highly likely diagnosis. EPS can manifest as various movement disorders, including parkinsonism, which is characterized by tremors or shaking.

Other Likely Diagnoses

• Anxiety or Stress-related Tremors: Given the patient's history of schizophrenia, episodes of shaking could be related to anxiety or stress, which are common in psychiatric conditions.
• Caffeine or Substance-induced Tremors: Consumption of caffeine or other substances can cause or exacerbate tremors, and patients with psychiatric conditions may have varying levels of substance use.
• Hypoglycemia: Although less common, hypoglycemic episodes can cause shaking or tremors, and patients on certain medications or with dietary restrictions are at higher risk.

Do Not Miss Diagnoses

• Neuroleptic Malignant Syndrome (NMS): A life-threatening, neurological disorder most often caused by an adverse reaction to neuroleptic or antipsychotic medication. It can present with muscle rigidity, fever, and changes in mental status, which might initially be mistaken for shaking or tremors.
• Serotonin Syndrome: Another potentially life-threatening condition that can occur with the use of certain medications, including some antipsychotics. It is characterized by a range of symptoms including agitation, confusion, rapid heart rate, and changes in blood pressure, which could initially present as episodes of shaking.
• Seizure Activity: Although the patient does not lose consciousness, certain types of seizures, such as simple partial seizures, can manifest as localized shaking or tremors without loss of consciousness.

Rare Diagnoses

• Wilson's Disease: A rare genetic disorder that leads to copper accumulation in the body, causing neurological symptoms including tremors. It's rare but should be considered in young patients with unexplained tremors and psychiatric symptoms.
• Thyroid Disorders: Both hyperthyroidism and hypothyroidism can cause tremors, although they would be accompanied by other systemic symptoms.
• Vitamin Deficiencies: Deficiencies in vitamins such as B12 can cause neurological symptoms, including tremors, though this would typically be part of a broader clinical picture.