Checking Motor and Sensory Level in Myelopathy

1. Motor level

• Test the key muscles for each myotome bilaterally (e.g., C5 deltoid/biceps, C6 wrist extensors, C7 triceps, C8 finger flexors, T1 finger abductors; L2 hip flexors, L3 knee extensors, L4 ankle dorsiflexors, L5 great toe extensors, S1 ankle plantarflexors).
• Grade each on the 0-5 MRC scale.
• The motor level is defined as the most caudal myotome with a grade of 3 or more, provided all myotomes rostral (above) to it grade 4 or 5 (normal or near-normal).
• In regions where there's no myotome to test (mid-thoracic cord, T2-L1), the motor level is presumed equal to the sensory level if motor function above that level is intact - Miller's Review of Orthopaedics, p. 794 (Rehabilitation after SCI).
• Do this separately for right and left sides, since levels can differ between sides (a Brown-Sequard-type pattern, for example).
• On top of segmental grading, look for the classic upper motor neuron signs below the lesion: spasticity, hyperreflexia, clonus, and a positive Babinski sign - these confirm a cord (not root) level and help distinguish myelopathy from radiculopathy.

2. Sensory level

• Test each dermatome bilaterally using two modalities:
  • Pinprick (spinothalamic tract - pain/temperature)
  • Light touch (dorsal column/posterior column pathways, along with proprioception and vibration)
• Score each dermatome as 0 (absent), 1 (impaired/altered), or 2 (normal).
• The sensory level is the most caudal dermatome that is normal (score 2) on both pinprick and light touch, with all dermatomes above it also normal.
• Test proprioception and vibration separately (posterior columns) since dorsal column deficits can appear before or independent of a clear pinprick level.
• Clinically, look for an abrupt change in sensation as you move the pin or touch stimulus down the trunk or limb - this "sensory level" is often several dermatomes caudal to the actual anatomical level of cord compression, so don't assume the sensory level equals the true lesion level.
• Always test both sides; asymmetric sensory levels (e.g., loss of pain/temperature on one side, loss of proprioception on the other) suggest a hemicord (Brown-Sequard) pattern.

3. Putting it together

• Neurological level of injury/lesion = the most caudal segment with both normal motor (grade ≥3, with normal grades above) and normal sensory function on both sides.
• In cervical myelopathy specifically (e.g., degenerative cervical myelopathy), also check for: Hoffmann sign, inverted radial reflex, Lhermitte sign, gait/tandem gait, and hand clumsiness (finger escape sign, grip-and-release test) - these support the diagnosis even when a discrete sensory level is subtle.
• Document findings using a standard chart (ASIA worksheet or equivalent) recording motor grade and sensory score for every myotome/dermatome bilaterally - this allows tracking progression or improvement over time, which matters greatly in myelopathy since decline can be gradual.

Practical bedside sequence

1. Cranial nerves and mental status (rule out higher lesion).
2. Motor exam of all key myotomes, both sides, MRC grading, note tone and any spasticity.
3. Reflexes: biceps, brachioradialis, triceps, knee, ankle, plus pathological reflexes (Babinski, Hoffmann, clonus).
4. Sensory exam: pinprick and light touch dermatome by dermatome, both sides, looking for the level where it changes; then proprioception/vibration at distal joints.
5. Gait and coordination (tandem gait, Romberg) since posterior column/corticospinal involvement often shows up here first in mild myelopathy.
6. Correlate with imaging (MRI) - the clinical level frequently sits below the true compressive level, so use it as a guide, not a precise map, for imaging localization and surgical planning.