Question

A patient presents with radicular pain radiating to the upper limb and spasticity in both lower limbs on examination. Where will be the level of lesion?

• A. C5
• B. C7
• C. C3
• D. C4

Hint:

Mixed neurological signs (LMN at the level of the lesion, UMN below the lesion) are the hallmark of compressive myelopathy. Radicular pain in the arm strictly points to a lower cervical (C5-T1) localization, excluding higher cervical (C3/C4) lesions.

Answer 1

The Correct Option is B

Concept:
The clinical scenario presents a patient exhibiting a classic mixed neurological picture: Lower Motor Neuron (LMN) signs at the level of the lesion (radicular pain to the upper limb) and Upper Motor Neuron (UMN) signs below the level of the lesion (spasticity in the lower limbs).
The task is to anatomically localize the spinal cord compression causing cervical myelopathy.
Explanation:
• When a compressive lesion (such as a herniated disc or cervical spondylosis) affects the spinal cord, it typically compresses the exiting nerve root at that specific level, while simultaneously compressing the descending long tracts (corticospinal tracts) traveling to lower segments.

• Compression of the exiting nerve root causes ipsilateral Lower Motor Neuron (LMN) signs in the specific dermatome/myotome supplied by that root. Radicular pain shooting down the arm indicates involvement of the brachial plexus roots (spanning from C5 to T1).

• Compression of the descending corticospinal tracts causes Upper Motor Neuron (UMN) signs (spasticity, hyperreflexia, Babinski sign) in all myotomes innervated below the level of the compression. Spasticity in the lower limbs confirms a UMN lesion above the lumbar level.

• A lesion at C3 or C4 would cause UMN signs in both the upper limbs (below the C4 level) and lower limbs, and would often involve diaphragmatic dysfunction, without typical brachial plexus radiculopathy.

• A lesion at the C7 level perfectly explains the presentation. It compresses the C7 nerve root, causing sharp radicular pain radiating down the arm (classically to the middle finger and affecting triceps strength), which is the LMN component. Simultaneously, it compresses the cord, leading to spastic paraparesis in the lower limbs, which is the UMN component.
Final Answer:
A lesion at the C7 spinal level best explains the combination of lower cervical radiculopathy (upper limb pain) and cervical myelopathy (lower limb spasticity).