Charcot-Marie-Tooth, MRI

Clinical History

A 14-year-old male patient presented with a history of life-long weakness, slight instability while walking with no associated falls, less physical aptitudes than his classmates and an uneven shoe wear.
Electrophysiological study shows motor and sensory polyneuropathy, mostly demyelinating, with severe and chronic axonal degeneration in upper and lower limbs.

Imaging Findings

Severe atrophy of extensor digitorum brevis muscles (EDB), dorsal and plantar interosseus and quadratus plantae (QP).
No flexor muscle disorders.
There was no evidence of muscle atrophy, fatty infiltration or oedema at any other muscle.

Discussion

Charcot–Marie–Tooth disease (CMTD), also known as hereditary motor and sensory neuropathy (HMSN), is the most frequent form of inherited polyneuropathy with a prevalence ratio of 17-40 cases per 100, 000 inhabitants.
CMTD is caused by different gene mutations that produce modified proteins that affect peripheral axon or myelin. That correlates with changes affecting the normal neuron function or structure. It can be transmitted autosomal dominant, autosomal recessive or X-linked.
There are many different types of CMTD. The most frequent form of CMTD is CMT1A (around 70%), that is an autosomal dominant disease caused by duplication of PMP22 [1, 2] and it arise as a disorder of peripheral myelination.
Symptoms are present during the first decade of life in over two thirds of cases. Foot deformity, basically forefoot pes cavus and considerably less frequently pes planus, is a cardinal manifestation of any form of CMT subtype, although significantly more common in CMT1 than in CMT2 patients. Sensory changes are present but usually to a lesser degree. [3]
Diagnosis process begins with the anamnesis of personal and family background and neurological examination. If CMTD is suspected, then electrophysiological study may be requested. Characteristically, motor conduction velocity in upper-limb nerves is <38 m/s in CMT1. [3]
During the last 8 - 10 years MRI is showing it usefulness for differential diagnosis: besides intrinsic foot muscle involvement, variable and distally accentuated fatty infiltration of the lateral, anterior, and superficial posterior leg muscle compartments and, to a lesser degree, of the deep posterior compartment [4]. Clinical MRI patterns of lower limb muscle atrophy vary with evolution of semiology. Selective involvement of intrinsic foot muscles is the characteristic pattern of CMT1A cases with minimal disease signs. Afterwards, this pattern usually combines variable and distally accentuated involvement of lower-leg muscles, especially those of the antero-lateral compartments.
The observed early selective fatty atrophy of intrinsic foot musculature, particularly of the lumbricals, in patients with mild phenotype but already showing pes cavus, supports its pathogenetic role in the initiation of forefoot pes cavus in CMT1A [5].
Positive diagnosis was traditionally made by peripheral nerve biopsy. Nowadays, it is made by genetic analysis. Genetic analysis can diagnose the existence of CMTD as well as it type.
There is no cure for CMTD, but physical therapy, orthotic and rehabilitation treatment or even orthopaedic surgery may be needed to help these patients to deal with the symptoms or disability caused by this disease.

Differential Diagnosis List

Final Diagnosis

Charcot-Marie-Tooth type 1A.

URL:	https://eurorad.org/case/14503
DOI:	10.1594/EURORAD/CASE.14503
ISSN:	1563-4086