What is the recommended imaging modality for a 60-year-old woman with suspected Motor Neuron Disease (MND) and symptoms including progressive proximal muscle weakness, atrophy, numbness, spasticity, and abnormal gait?

MRI Cervical Spine is the Recommended Imaging Modality for Suspected Motor Neuron Disease

MRI of the cervical spine without IV contrast is the recommended imaging modality for a 60-year-old woman with suspected Motor Neuron Disease (MND) presenting with progressive proximal muscle weakness, atrophy, numbness, spasticity, and abnormal gait. 1

Rationale for Cervical Spine MRI in MND

MRI imaging in suspected MND serves primarily to exclude other conditions with similar clinical presentations rather than to confirm the diagnosis of MND itself. The cervical spine MRI is particularly valuable because:

• It can detect the characteristic "snake eyes" appearance (abnormal T2/STIR signal in the anterior horns) which corresponds to lateral corticospinal tract involvement and reflects lower motor neuron disease 1
• It helps exclude structural, infectious, or neoplastic etiologies of the spine that can mimic motor neuron disease 1
• It provides superior soft-tissue characterization compared to CT, which is essential for evaluating the spinal cord 1

Imaging Algorithm for Suspected MND

1. First-line imaging: MRI cervical spine without IV contrast

   • Allows visualization of potential anterior horn abnormalities
   • Can detect cord compression or other structural lesions that might mimic MND

2. Additional imaging when indicated:

   • MRI brain without IV contrast may be appropriate to evaluate upper motor neuron involvement 1
   • This can show abnormal signal on T2/FLAIR in the corticospinal tracts and hypointensity in the precentral gyrus on T2*/SWI sequences 1

Key MRI Findings in MND

• Cervical spine:

  • Abnormal T2/STIR hyperintensity in the anterior horns ("snake eyes" appearance) 1
  • This finding may only be present later in the disease course and is not specific for MND alone 1

• Brain (if performed):

  • Abnormal signal on T2/FLAIR along corticospinal tracts from subcortical white matter to pons 1
  • T2*/SWI hypointensity in the precentral gyrus 1

Important Considerations

• MRI findings may be normal early in the disease course of MND 1
• Electromyography and nerve conduction velocity studies remain key diagnostic tests for MND, with imaging primarily used to exclude mimics 1
• Advanced MRI techniques like diffusion tensor imaging (DTI) may show bilateral impairment of corticospinal tract diffusion metrics even when conventional MRI appears normal 2

Imaging Modalities to Avoid

• CT of the spine: Not useful in diagnosing MND due to limited soft-tissue characterization 1
• FDG-PET/CT brain: No relevant literature supports its use in the initial evaluation of suspected MND 1
• MR spectroscopy or functional MRI: Not supported by evidence for initial evaluation of suspected MND 1

Clinical Pearls

• The diagnosis of MND should not be made based on imaging alone but requires correlation with clinical findings and electrophysiological studies
• When MND presents with isolated limb symptoms (as in this case), cervical spine MRI is particularly important to rule out structural lesions that could be treatable
• Subacute presentation of symptoms may raise suspicion of ischemic or inflammatory etiology rather than degenerative disease, making imaging crucial for differential diagnosis 2