What new sensory deficit would a patient with Multiple Sclerosis (MS) most likely report with a new demyelinating plaque at C4 on the right side of the cervical spine?

Sensory Deficit in Multiple Sclerosis with C4 Demyelinating Plaque

A patient with a demyelinating plaque on the right lateral edge of the spinal cord at C4 would most likely report contralateral (left-sided) pain and temperature sensation loss below the level of the lesion.

Anatomical Basis for the Sensory Deficit

• The spinothalamic tract carries pain and temperature sensations from the body to the brain 1
• Fibers in the spinothalamic tract cross (decussate) to the opposite side at the level they enter the spinal cord, then ascend in the contralateral spinothalamic tract 1
• A lesion affecting the lateral spinothalamic tract at C4 on the right side would therefore affect sensations coming from the left side of the body below the level of the lesion 1

Expected Clinical Manifestations

• The patient would likely report decreased pain and temperature sensation on the left side of the body below the C4 dermatome 1
• This would manifest as decreased sensation to pinprick and temperature in the left arm, trunk, and leg 1
• Proprioception and vibration sense (carried in the dorsal columns) would likely be preserved unless the lesion extends medially 1
• Light touch may be partially affected but is often preserved due to redundant pathways 1

Somatotopy of the Spinothalamic Tract

• The spinothalamic tract has a specific somatotopic organization with fibers from the lower extremities positioned more laterally 1
• Since this plaque is described as being on the lateral edge of the cord, it may preferentially affect sensation from the lower extremities on the contralateral side 1
• The small size of the plaque suggests the deficit might be partial rather than complete 1

Relevance to Multiple Sclerosis

• MS commonly affects the cervical spinal cord, with 80-90% of MS patients showing cervical cord involvement 1
• Demyelinating plaques in MS can affect any part of the central nervous system, including the spinal cord tracts 1, 2
• The sensory deficit pattern helps localize the lesion and can be correlated with MRI findings to confirm the relationship between the structural lesion and clinical symptoms 1

Clinical Assessment Considerations

• Careful sensory testing should be performed to map the exact distribution of sensory loss 1
• The clinician should specifically test for pinprick and temperature sensation on both sides of the body to detect the contralateral deficit 1
• The presence of this specific sensory deficit pattern can help distinguish MS from other conditions that might cause similar symptoms 1, 2

Potential Pitfalls in Assessment

• Multiple lesions may be present in MS, potentially causing overlapping or confusing sensory patterns 1, 2
• Patients may have difficulty precisely describing sensory changes, requiring careful and systematic examination 1
• The small size of the lesion might cause subtle deficits that could be missed without thorough testing 1