What is the most appropriate next investigation for a 65-year-old male with recurrent bouts of unsteadiness, vomiting, visual problems, ataxic gait, spasticity, and exaggerated reflexes, with MRI brain showing diffuse lesions?

Most Appropriate Next Investigation for a 65-Year-Old Male with Neurological Symptoms

MRI of the spinal cord (Option A) is the most appropriate next investigation for this patient with suspected multiple sclerosis presenting with recurrent neurological symptoms and MRI brain showing diffuse lesions.

Clinical Presentation Analysis

This 65-year-old male presents with:

• Recurrent bouts of unsteadiness and vomiting over 10 years
• Episodes of visual problems (transient right eye vision loss with partial recovery)
• Ataxic gait
• Spasticity in both lower limbs
• Exaggerated reflexes and bilateral ankle clonus
• Nystagmus in the right eye
• Pale optic disc on fundoscopic examination
• MRI brain showing diffuse lesions in multiple sites (possibly demyelinating plaques vs. multiple infarcts)

Diagnostic Reasoning

Why MRI Spinal Cord is the Best Choice:

1. Evidence of Spinal Cord Involvement: The patient's clinical presentation strongly suggests spinal cord involvement:

   • Spasticity in both lower limbs
   • Exaggerated reflexes and bilateral ankle clonus
   • Ataxic gait

2. Guideline-Based Recommendation: The ACR Appropriateness Criteria for Ataxia recommends MRI of the spine when there are additional signs of spinal cord involvement 1. For patients with chronic disequilibrium with signs of cerebellar ataxia, MRI cervical and thoracic spine is indicated to evaluate for spinal cord atrophy or other pathology.

3. Differentiation Between MS and Vascular Disease: The MRI brain report suggests either demyelinating plaques or multiple infarcts. Spinal MRI can help differentiate between these two possibilities:

   • Multiple sclerosis typically shows characteristic lesions in the spinal cord
   • Vascular disease rarely affects the spinal cord in the same pattern as MS

4. Assessment of Disease Burden: In demyelinating disorders, MRI of the spine helps assess the disease burden and can help differentiate different acquired demyelinating disorders (neuromyelitis optica spectrum disorders versus multiple sclerosis) 1, 2.

Why Other Options Are Less Appropriate:

• CSF examination for oligoclonal bands (Option B): While useful for confirming MS, this should follow spinal imaging given the clear signs of spinal cord involvement.

• MR angiography of the vertebrobasilar system (Option C): Although the patient has vascular risk factors (diabetes, hypertension, smoking), the ACR guidelines state that "There is no evidence to support the use of MRA as the initial imaging test for ataxia with no history of trauma" 1.

• Titres of anti-Hu antibodies (Option D): These are associated with paraneoplastic syndromes, but the clinical presentation is more consistent with demyelinating disease or vascular disease rather than paraneoplastic syndrome.

• Visual evoked potentials (Option E): While relevant for assessing optic nerve function, this test is less critical than spinal imaging given the clear signs of spinal cord involvement.

Clinical Implications

MRI of the spinal cord will:

• Confirm the presence of spinal cord lesions characteristic of MS
• Help differentiate between MS and vascular disease
• Assess for longitudinally extensive transverse myelitis, which would suggest neuromyelitis optica spectrum disorder rather than MS
• Guide appropriate treatment decisions

Common Pitfalls to Avoid

1. Focusing only on brain imaging: In patients with both brain and spinal cord symptoms, comprehensive evaluation requires imaging of both areas.

2. Attributing all symptoms to vascular disease: Despite the patient's vascular risk factors, the clinical presentation is more consistent with demyelinating disease.

3. Delaying spinal imaging: Early diagnosis of MS or other demyelinating disorders is crucial for initiating appropriate treatment and potentially slowing disease progression.

4. Overlooking the value of spinal imaging: MRI of the spine allows for evaluation of the spinal column as well as the soft tissues within and surrounding the spinal column including the spinal cord 1, 3, 4.

By proceeding with MRI of the spinal cord, you will obtain the most valuable diagnostic information to guide further management of this patient with complex neurological symptoms.