What should I order to follow up on a patient with Huntington's disease presenting with increased confusion and dysarthria?

Diagnostic Workup for Huntington's Disease Patient with Increased Confusion and Dysarthria

For a patient with Huntington's disease presenting with increased confusion and dysarthria, brain MRI without contrast is the optimal initial diagnostic test to evaluate for disease progression and rule out other causes of symptom worsening. 1

Primary Diagnostic Tests

1. Brain MRI without contrast:

   • Evaluates for progressive striatal atrophy (particularly caudate nucleus)
   • Detects abnormal signal changes in the basal ganglia
   • Rules out other structural causes of worsening symptoms 1

2. Laboratory tests:

   • Complete blood count
   • Comprehensive metabolic panel (including liver and kidney function)
   • Calcium, magnesium levels (to rule out electrolyte disturbances)
   • Ammonia level (to assess for hepatic encephalopathy)
   • Thyroid function tests 1

Secondary Evaluations

Neurological Assessment

• Formal neurological evaluation by a neurologist or movement disorder specialist 1
• Cognitive assessment using standardized tools:
  • Cognitive Linguistic Quick Test (15-30 minutes)
  • Assessment of language and dysarthria using Dysarthria Examination Battery 1

Medication Review

• Evaluate current medications, particularly:
  • Tetrabenazine dosing (may cause sedation, parkinsonism, depression) 2
  • Benzodiazepines (contraindicated in patients with encephalopathy) 1
  • Antipsychotics (may worsen parkinsonism features)

Differential Diagnosis Considerations

The worsening confusion and dysarthria in a Huntington's disease patient could represent:

1. HD disease progression - most common cause
2. Medication side effects - particularly from tetrabenazine (dysarthria occurs in 4% of patients) 2
3. Hepatic encephalopathy - consider in patients with liver dysfunction 1
4. Metabolic disturbances - electrolyte abnormalities, hypoglycemia 1
5. Cerebrovascular event - stroke or TIA
6. Infection - particularly urinary tract or respiratory

Clinical Pearls and Pitfalls

• Important: Dysarthria is a known component of HD progression but can also be a medication side effect. In a 12-week study, dysarthria was observed in 4% of tetrabenazine-treated patients 2
• Caution: Tetrabenazine can cause sedation in 31% of patients and parkinsonism in 9%, which may mimic disease progression 2
• Remember: Worsening confusion may represent psychiatric manifestations of HD but should prompt evaluation for reversible causes first
• Consider: Many HD patients receive lower than optimal tetrabenazine doses due to side effects (66.5% receive ≤50 mg) 3

Follow-up Recommendations

After diagnostic workup:

1. Adjust medications as needed based on findings
2. Consider speech therapy referral for dysarthria management
3. Schedule follow-up neurological evaluation to monitor response
4. Provide caregiver education about disease progression and symptom management

This structured approach will help determine whether the patient's symptoms represent disease progression or potentially reversible causes that require specific interventions.