Polyneuropathy - Charcot Marie Tooth

 

Thank you for asking me to examine Mr. X, who presented difficulty walking.

 

The most salient findings on examination were an ataxia with a broad base (if proprioception lost), stamping, as well as high stepping gait, with pes cavus and distal atrophy, with an associated symmetrical weakness without upper motor neuron signs which would be most consistent with a hereditary neuropathy such as Charcot Marie Tooth. (or to keep it broad initially before committing - ‘which is suggestive of a motor predominant peripheral neuropathy / sensorimotor neuropathy, however there are other differentials which I will discuss after my presenting my findings in full’)

 

In further detail...

 

On inspection the patient was comfortable and did / did not have any gait aids. There were/were not any shoe or ankle supports.

 

The gait was ataxic and broad-based with stamping (proprioception loss) and high stepping (due to foot drop from distal motor neuropathy). The patient could/could not walk heel to toe, suggesting the presence/absence of a cerebellar pathology. The patient could/could not walk on their toes (S1), and the heels (foot drop, L4 or L5). Romberg’s sign was/was not positive (eyes closed - posterior columns, eyes open - cerebellar).

 

There were/were no scars on the back.

 

On inspection of the legs, there were/were not scars. There was distal wasting of the lower limbs, especially of the anterolateral muscle compartment with relative preservation of the thigh musculature, giving an inverted champagne bottle appearance. There was bilateral pes cavus and clawing of the toes

 

There was not muscle tenderness. Tone was reduced/increased/normal in the knee and ankle, and there was/was not clonus. There was an enlarged common peroneal nerve (CMT).

 

Power was reduced symmetrical with __/5 power on the left leg, and __/5 power on the right.

 

Reflexes were absent in the knee and ankle with no plantar response.

 

Coordination was normal on heel-shin, toe-finger and foot tapping assessment.

 

Sensation was reduced/normal symmetrically in a stocking distribution, with reduced sensation to vibrations sensation to ___ and proprioception to the ___. Pain sensation was normal/impaired (often normal).

 

In summary this patient has symmetrical distal weakness with lower motor neuron signs, which is likely long standing given the presence of pes cavus and severe atrophy and suggests a hereditary neuropathy such as Charcot-Marie-Tooth.

 

Differentials for symmetrical distal weakness with LMN signs include:

• Peripheral neuropathy

• NMJ - less likely as wasting and absent reflexes

• Myopathy

  • Less likely as distal

  • Reflexes generally preserved

  • Sensation preserved

  • No fasciculations

• Anterior horn cell disease

 

Differential for a sensorimotor neuropathy include:

• Metabolic causes - primarily diabetes, CKD/uraemia, thyroid

• Drug and alcohol related - vincristine, cisplatinum

• B12

• Immune mediate such as GB and CIDP - however, typically these have less sensory involvement, and no pes cavus, and are non-length dependent with proximal and distal muscles affected similarly

• Paraneoplastic - tumour, or paraproteinemia

• Connective tissue disease and vasculitis

• Idiopathic

 

Differential for a predominately motor neuropathy include:

• GBS/CIDP

• Hereditary motor and sensory neuropathy - CMT

• Diabetes

• Multifocal motor neuropathy

• Other - porphyria, lead, diphtheria, drugs (dapsone)

 

I would proceed from here by:

• Confirming my diagnosis with nerve conduction studies (low conduction velocity, low amplitude if axonal)

• Assessing for other aetiology by:

  • History

  • Screen for diabetes, CKD, thyroid function

 

Nerve conduction studies:

Nerve conduction studies in CIDP typically show nonuniform, nonhomogeneous slowing with partial or complete conduction blocks. This finding can help differentiate CIDP from CMT, since nerve conduction slowing in the demyelinating forms of CMT is typically diffuse and homogeneous