What cervical nerve root is most responsible for pain and numbness down the back of the tricep, top of forearm, and middle finger?

C7 Nerve Root is Most Responsible for Pain and Numbness Down Back of Tricep, Top of Forearm and Middle Finger

The C7 nerve root is most likely responsible for the pattern of pain and numbness down the back of the tricep, top of forearm, and middle finger.

Dermatome and Myotome Patterns in Cervical Radiculopathy

Cervical radiculopathy presents with specific patterns of sensory and motor symptoms based on the affected nerve root. When evaluating the described symptoms:

• C7 nerve root compression typically causes:
  • Pain/numbness along the posterior aspect of the arm (tricep area)
  • Sensory changes along the dorsal (top) aspect of the forearm
  • Sensory changes in the middle finger
  • Weakness in the triceps muscle

Differentiating C6 vs C7 Radiculopathy

While there is significant overlap in symptom presentation between C6 and C7 radiculopathies, some key distinctions can be made:

• C6 radiculopathy typically affects:

  • Lateral aspect of the forearm
  • Thumb and index finger
  • Biceps and wrist extensors

• C7 radiculopathy typically affects:

  • Posterior arm (tricep area)
  • Middle finger
  • Triceps and wrist flexors

Research shows considerable overlap in sensory distributions, making clinical differentiation challenging. According to studies examining MRI-confirmed radiculopathies, the sensory distributions of C6 and C7 overlap extensively, with the main difference being that impaired sensation in the radial aspect of the distal forearm is twice as common in C6 radiculopathy 1.

Diagnostic Approach

When evaluating suspected cervical radiculopathy:

1. Clinical examination:

   • Spurling test (neck extension and lateral rotation toward the affected side)
   • Shoulder abduction test
   • Upper limb tension test

2. Imaging:

   • MRI is the preferred method for evaluating cervical nerve root impingement due to its superior soft-tissue contrast and spatial resolution 2
   • CT may be helpful for assessing bony foraminal stenosis but is less sensitive than MRI for nerve root compression 2

3. Electrodiagnostic testing:

   • Not needed if diagnosis is clear
   • Useful when peripheral neuropathy is a possible alternative diagnosis 3

Clinical Pearls and Pitfalls

• Important caveat: The location of sensory impairments for C6 and C7 radiculopathies overlap significantly, making it difficult to definitively determine the affected root based solely on sensory symptoms 4

• Diagnostic challenge: Studies show that the correlation between clinical neurological findings/dermatome pain distribution and the actual compressed nerve root (as confirmed by selective nerve root blocks) is only about 28% 5

• Reflex examination: Diminished triceps reflex is most commonly associated with C7 radiculopathy, while diminished brachioradialis reflex is more common with C6 radiculopathy

• Motor examination: Weakness in triceps extension suggests C7 involvement, while weakness in wrist extension or biceps suggests C6 involvement

The pattern described in the question (posterior tricep, dorsal forearm, middle finger) most closely aligns with the C7 dermatome, though clinical correlation with physical examination findings and possibly imaging would be needed for definitive diagnosis.