What investigations should be completed for a patient on antipsychotics with chronic dizziness and hyponatremia who sustained a fall due to dizziness?

Comprehensive Investigations for a 63-Year-Old Male on Antipsychotics with Chronic Dizziness, Hyponatremia, and Fall

For a 63-year-old male on antipsychotics with chronic dizziness, chronic hyponatremia who fell due to dizziness, a comprehensive neurological evaluation, vestibular assessment, and electrolyte workup should be prioritized to identify the underlying cause and prevent future falls.

Initial Evaluation

• Obtain serum sodium level to assess severity of hyponatremia (< 135 mEq/L) and determine if acute (< 48 hours) or chronic (> 48 hours) 1, 2
• Complete neurological examination and Dix-Hallpike test to identify possible benign paroxysmal positional vertigo (BPPV) as a cause of dizziness 1
• Assess for signs of delirium using standardized screening tools, as antipsychotics can cause hyponatremia and contribute to falls 1, 3
• Perform a falls risk assessment using validated tools such as Get Up and Go test, Tinetti Balance Assessment, or Berg Balance Scale 1

Electrolyte and Fluid Status Workup

• Measure serum and urine osmolarity to differentiate between different causes of hyponatremia 1
• Obtain urine electrolytes and uric acid to help determine volume status 1
• Evaluate extracellular fluid (ECF) volume status to categorize hyponatremia as hypovolemic, euvolemic, or hypervolemic 1
• Check thyroid function and cortisol levels to rule out endocrine causes of hyponatremia 1

Medication Review

• Review all antipsychotic medications as they are associated with hyponatremia (ROR 1.58,95% CI 1.46-1.70) 4
• Assess for concomitant medications that may worsen hyponatremia (ROR increases to 3.00,95% CI 2.65-3.39 when no other medications associated with hyponatremia are present) 4
• Evaluate anticonvulsant medications if present, as they can also cause hyponatremia 2

Vestibular and Balance Assessment

• Perform a complete vestibular examination to identify peripheral versus central causes of dizziness 1
• Consider specialized vestibular testing if initial examination suggests vestibular dysfunction 1
• Assess gait and balance to determine fall risk and need for assistive devices 1

Neuroimaging and Additional Tests

• Brain imaging (CT or MRI) to rule out stroke or other central nervous system disorders, especially important since brainstem and cerebellar strokes can present similar to peripheral vestibular disorders in 10% of cases 1
• Electroencephalogram (EEG) if there are concerns about seizures or non-convulsive status epilepticus, particularly in patients with altered mental status 1
• Consider electrocardiogram (ECG) to evaluate for cardiac causes of dizziness or falls 1

Management Considerations

• Correction of hyponatremia should be based on severity of symptoms and chronicity - acute symptomatic hyponatremia may require more rapid correction (up to 6 mmol/L in first 6 hours) while chronic hyponatremia should be corrected more slowly 1
• Total correction of sodium should not exceed 8 mmol/L over 24 hours to prevent osmotic demyelination syndrome 1
• Consider treatment of BPPV with canalith repositioning procedures if diagnosed 1
• Evaluate need for modification of antipsychotic regimen if contributing to hyponatremia 3, 4

Special Considerations

• Hyponatremia in elderly patients with falls is associated with worse outcomes, including longer hospital stays, higher ICU admission rates, and increased mortality 5
• Elderly patients with hyponatremia have 12-fold increased risk for falls compared to those without hyponatremia 6
• Patients on antipsychotics with hyponatremia may develop symptoms including lethargy, dizziness, weakness, headache, nausea, and confusion in chronic cases, or delirium and seizures in acute cases 2
• The average time to hyponatremia events with second-generation antipsychotics is approximately 17 days, with average sodium levels dropping from 138 mmol/L to 112 mmol/L 3

Follow-up Recommendations

• Monitor serum sodium levels regularly during hospitalization and after discharge 2, 6
• Implement fall prevention strategies before discharge 1, 6
• Ensure hyponatremia is corrected prior to discharge and arrange close follow-up with primary care physician 6
• Consider referral to vestibular rehabilitation if vestibular dysfunction is identified 1