Symptoms of Unilateral C7 Lesion
The symptom a patient with a unilateral C7 lesion is least likely to present with is loss of temperature sensation on the same side (ipsilateral) as the lesion.
Pathophysiology of C7 Lesions
A unilateral C7 lesion affects the seventh cervical nerve root or its corresponding level in the spinal cord. Understanding the expected clinical manifestations requires knowledge of the neuroanatomy at this level:
Expected Findings in Unilateral C7 Lesion:
Weakness of Triceps
- C7 innervates the triceps muscle, so weakness is an expected finding 1
- Triceps weakness is a classic manifestation of C7 radiculopathy
Loss of Abdominal Reflexes Below the Lesion
- Abdominal reflexes are mediated by thoracic segments but can be affected by cervical lesions due to descending pathway disruption
- A unilateral C7 lesion can cause loss of abdominal reflexes below the level of the lesion on the same side
Loss of Proprioception Below the Lesion
- Proprioceptive information travels in the posterior columns on the same side of the spinal cord
- A C7 lesion would affect proprioception on the ipsilateral side below the level of the lesion
Positive Hoffman Sign
- This is a sign of upper motor neuron dysfunction
- Can be present with cervical cord compression at the C7 level due to disruption of descending corticospinal tracts
Why Temperature Sensation Loss on Same Side is Incorrect:
Temperature sensation fibers cross shortly after entering the spinal cord and ascend in the contralateral spinothalamic tract. Therefore:
- A unilateral C7 lesion would cause loss of temperature sensation on the opposite side (contralateral) of the body below the level of the lesion
- Temperature sensation loss on the same side as the lesion would not be expected
Clinical Presentation of C7 Radiculopathy
C7 radiculopathy has specific clinical manifestations:
- Pain and sensory changes typically affect the posterior arm, dorsal forearm, and middle finger 2
- Weakness primarily affects the triceps muscle and wrist extensors
- Diminished triceps reflex is common
- Atypical presentations may include subscapular pain (12% of cases) or chest/breast pain (5% of cases) 3
Diagnostic Considerations
When evaluating a patient with suspected C7 lesion:
- MRI is the preferred imaging modality for suspected cervical radiculopathy 1
- Sensory examination alone has limited value in distinguishing C6 from C7 radiculopathy, as there is significant overlap in sensory distributions 2
- Weakness of the triceps muscle is a more reliable indicator of C7 involvement than sensory changes
Summary
In a unilateral C7 lesion, you would expect:
- Ipsilateral triceps weakness
- Ipsilateral loss of proprioception below the lesion
- Ipsilateral loss of abdominal reflexes below the lesion
- Positive Hoffman sign
- Contralateral (not ipsilateral) loss of temperature sensation below the lesion
Therefore, loss of temperature sensation on the same side as the lesion is the least likely finding among the options provided.