What is the next step in evaluating a patient with recurrent episodes of slurred speech, mild dysmetria, and mild hypertonicity in the legs, with normal computed tomography (CT) of the head and normal comprehensive metabolic panel (CMP) and complete blood count (CBC)?

MRI of the Brain and Spine Should Be Ordered Now

For this 39-year-old woman with recurrent neurological episodes (slurred speech, dysmetria, hypertonicity) and normal CT head, MRI of the brain and spine is the appropriate next diagnostic step to evaluate for demyelinating disease, particularly multiple sclerosis. 1

Clinical Reasoning

Why MRI is Essential in This Case

• Recurrent episodes with complete resolution between attacks strongly suggest a relapsing-remitting demyelinating process, most commonly multiple sclerosis 1
• Multifocal neurological findings (dysarthria, cerebellar signs with dysmetria, and upper motor neuron signs with leg hypertonicity) indicate lesions in different CNS locations, which is characteristic of demyelinating disease 1
• Normal CT does not exclude demyelinating disease, as CT has poor sensitivity for detecting white matter lesions and posterior fossa pathology due to beam hardening artifacts 2, 3
• MRI detects early disease with increased water content (including multiple sclerosis plaques, early infarcts, and inflammatory lesions) with far greater sensitivity than CT 2, 4

Why Spine Imaging is Critical

• Spinal cord involvement occurs in 15-20% of MS patients with normal or minimal brain MRI findings 1
• In a study of 20 patients with suspected MS and minimal/no brain abnormalities, all had spinal cord lesions visible on MRI (median 2 lesions, range 1-6) 1
• Patients presenting with spinal cord symptoms (as suggested by leg hypertonicity in this case) particularly benefit from spinal imaging 1
• Combined brain and spine MRI increases diagnostic yield when brain MRI alone may be insufficient 1

Why Other Options Are Inappropriate

Cerebrospinal Fluid Oligoclonal Bands (Option A)

• Premature without imaging first - CSF analysis should follow, not precede, neuroimaging in suspected demyelinating disease 5
• Oligoclonal bands support but do not establish the diagnosis without demonstrating dissemination in space via imaging 1
• Lumbar puncture carries procedural risks and should be reserved for cases where imaging is equivocal 5

Electroencephalogram (Option C)

• EEG has no role in evaluating dysmetria and hypertonicity - these are not seizure-related symptoms 5
• The clinical presentation (focal neurological deficits with clear consciousness, gradual onset over hours, prior similar episode) is inconsistent with seizure activity 5
• EEG would only be indicated if there were concerns about altered consciousness or episodic loss of awareness 5

No Further Testing (Option D)

• Dangerous and inappropriate given recurrent neurological symptoms with objective findings on examination 5, 1
• The patient has persistent symptoms (6 hours without improvement) and documented neurological deficits requiring explanation 5
• Early diagnosis of demyelinating disease allows for disease-modifying therapy that can reduce disability progression 1

MRI Technical Considerations

• Spin-echo sequences with long multiple echoes provide sensitive detection with sufficient tissue characterization for diagnosis 4
• T2-weighted and FLAIR sequences are particularly sensitive for detecting demyelinating plaques 2, 3
• Gadolinium contrast may be added if initial sequences suggest demyelination, to assess for active inflammation and blood-brain barrier breakdown 6
• MRI is superior in the posterior fossa where this patient's cerebellar signs (dysmetria) localize 2, 3

Critical Pitfalls to Avoid

• Do not assume normal CT excludes serious pathology - CT misses most white matter diseases and posterior fossa lesions 2, 3
• Do not delay MRI to perform CSF studies first - imaging should guide the decision about whether lumbar puncture is needed 5
• Do not image only the brain - approximately 15-20% of MS patients with minimal brain findings have diagnostic spinal lesions 1
• Do not dismiss recurrent symptoms as functional when objective neurological signs are present on examination 1

The combination of recurrent episodes, multifocal CNS signs, young age, and normal CT makes demyelinating disease the leading diagnosis, and MRI of brain and spine is the definitive test to establish this diagnosis 2, 3, 4, 1.