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Hypertrophic Neuropathy


KEY FACTS

Terminology

  • Group of inherited disorders characterized by focal or diffuse peripheral nerve enlargement

  • Hereditary motor-sensory neuropathy (HMSN), hypertrophic neuropathy (HN), hereditary sensory neuropathy (HSN), hereditary motor neuropathy (HMN), hereditary sensory and autonomic neuropathy (HSAN), Charcot-Marie-Tooth (CMT) syndrome

Imaging

  • Focal or diffuse fusiform peripheral nerve enlargement

    • Peripheral nerves ± intradural nerve roots

    • ± involvement of cauda equina nerve roots

  • Acute &/or chronic muscle denervation changes

  • Best imaging tool: High-resolution MR (MR neurography)

Top Differential Diagnoses

  • Guillain-Barré syndrome

  • Chronic inflammatory demyelinating polyneuropathy

  • Nerve sheath tumor

  • Traumatic nerve stretch injury

Pathology

  • Hypertrophic nerve roots, peripheral nerves

  • “Onion bulb” formations = nerve thickening caused by repetitive segmental demyelination/regeneration (histologic hallmark of CMT but can occur in others)

Clinical Issues

  • Distal extremity muscle weakness/atrophy (motor > sensory), foot deformities

  • Back/lower extremity radicular pain ± myelopathy

  • Sensory loss, focal tenderness, dysesthesias

  • ± palpable nerve mass

Diagnostic Checklist

  • Consider HMSN when abnormally enlarged peripheral nerves identified on MR

  • Genetic consultation recommended for patients with fusiform nerve enlargement on MR

Coronal T1WI MR (Charcot-Marie-Tooth, painful scoliosis) demonstrates convex left scoliosis
and bilateral abnormal fusiform enlargement of the extradural spinal nerve roots and lumbar plexus
.

Axial T2WI MR (Charcot-Marie-Tooth, painful scoliosis) confirms abnormal enlargement and T2 hyperintensity of the bilateral extradural lumbar nerve roots
as well as aberrant enlargement of the intradural cauda equina nerve roots
.

Coronal STIR MR (unknown type hypertrophic neuropathy, left arm pain and weakness) demonstrates abnormal fusiform enlargement of the left proximal brachial plexus C7 and C8 roots/rami
.

Coronal T1WI C+ FS MR of the left brachial plexus in the same patient confirms fusiform enlargement and diffuse homogeneous nerve enhancement within the left proximal brachial plexus C7 and C8 roots/rami
.

TERMINOLOGY

Synonyms

  • Hereditary motor-sensory neuropathy (HMSN), hypertrophic neuropathy (HN), hereditary sensory neuropathy (HSN), hereditary motor neuropathy (HMN), hereditary sensory and autonomic neuropathy (HSAN), Charcot-Marie-Tooth (CMT) syndrome

Definitions

  • Clinically and genetically heterogeneous group of inherited disorders characterized by focal or diffuse peripheral nerve enlargement

  • Subdivided into 3 main categories based on predominant involvement of motor &/or sensory nerves

    • Both motor and sensory nerves affected → HMSN

      • –

        HMSN I (Charcot-Marie-Tooth syndrome type I, CMT 1)

      • –

        HMSN II (neuronal-type peroneal muscular atrophy, CMT 2)

      • –

        HMSN III (Dejerine-Sottas disease [DSD], hypertrophic neuropathy of infancy, congenital hypomyelinating neuropathy)

    • Motor nerve fibers primarily → distal HMN, spinal CMT, distal spinal muscular atrophy

    • Mainly peripheral sensory ± autonomic nerves → hereditary sensory neuropathy (HSN) or hereditary sensory and autonomic neuropathy (HSAN)

IMAGING

General Features

  • Best diagnostic clue

    • Focal or diffuse peripheral nerve enlargement + distal extremity atrophy

  • Location

    • Peripheral nerves ± intradural nerve roots

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