Myotomes Lower Limb | Peripheral Neurological Examination

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Myotomes Lower Limb | Peripheral Neurological Examination

Myotome assessment is an essential part of neurological examination when suspecting radiculopathy, as changes in muscle strength within a specific myotome may help you identify the pathological disc level. Al Nezari et al. (2013) performed a systematic review and meta-analysis of 14 different studies investigating sensory, motor, and reflex testing for lumbar disc herniations. The results showed that testing for paresis in myotomes had 22-40% sensitivity and 62-79 percent specificity which corresponds to a sensitivity of 31% and a specificity of 76%in the identification of the pathological disk level. The pooled positive likelihood ratios for all neurological examination components range between 1.02 and 1.26. So positive or negative findings don’t raise the post-test probability much at all which is why we attribute this assessment a rather weak clinical value.

Despite these findings, it’s still the best tool we have in physical assessment. Myotome testing of the lower extremity is done with the patient in supine lying position. As with sensory assessment, you should compare the affected and unaffected side.

L2 = hip flexion
L3 : Hip Extension
L4: Tibialis Anterior / ankle dorsiflexion
L5: Extensor Hallucis Longus / Great Toe Extension
S1: Calf Muscles / Ask the Patient to perform a calf raise (several times)
Even though nerve root pathology is very rare on sacral level S2, weakness in knee flexion would indicate such compromise.