Selective calf weakness suggests intraspinal pathology, not peripheral neuropathy

Area of Science:

• Neurology
• Neuroscience
• Clinical Medicine

Background:

• Peripheral neuropathy is a common neurological disorder affecting nerve function outside the brain and spinal cord.
• Distinguishing peripheral neuropathy from intraspinal conditions is crucial for appropriate patient management.
• Heel-walking ability (plantarflexion) versus toe-walking ability (dorsiflexion) can provide diagnostic clues.

Observation:

• Four patients presenting with symptoms suggestive of peripheral neuropathy demonstrated an unusual pattern: they could walk on their heels but not on their toes.
• In all four patients, diagnostic investigations revealed intraspinal pathologies, including ependymoma of the filum terminale, spinal muscular atrophy, spinal stenosis, and meningeal carcinomatosis.
• This contrasts with 86 cases of hereditary motor and sensory neuropathy type 1, where plantar flexors were not weaker than dorsiflexors.

Findings:

• A key clinical finding is that patients exhibiting greater weakness in plantar flexor muscles (inability to walk on toes) compared to dorsiflexor muscles (ability to walk on heels) should raise suspicion for intraspinal disease.
• This specific pattern of muscle weakness is a potential indicator differentiating intraspinal pathology from typical peripheral neuropathies.
• Physiological and biomechanical factors are proposed to explain why peroneal nerve-innervated muscles might exhibit differential weakness in peripheral neuropathy.

Implications:

• The study suggests a novel clinical sign for identifying intraspinal disease, potentially aiding in earlier diagnosis and intervention.
• This finding challenges the assumption that heel-walking preservation with toe-walking weakness solely indicates peripheral nerve issues.
• Further research into the biomechanics and neurophysiology of gait abnormalities in spinal cord versus peripheral nerve disorders is warranted.