Musculoskeletal ImagingNeuropathy
a disorder of the peripheral nervous system that may be functional or structural. Numerous types of neuropathies occur.
Peripheral neuropathies are primary disorders of peripheral motor, sensory and autonomic neurons and can be classified as mononeuropathies, multiple mononeuropathies and polyneuropathies depending on number of nerves involved (Fig.1). These disorders are accompanied by muscle weakness, muscle atrophy, sensory change, autonomic dysfunction or any combination of these. Among the most common abnormalities are entrapment neuropathies resulting from compression of a segment of a nerve at a specific site, often as it passes through a fibro-osseous tunnel or an opening in fibrous or muscular tissue. Numerous nerves are subject to entrapment, including the median, ulnar, radial, musculocutaneous, suprascapular, dorsoscapular or brachial plexus nerves in the upper extremities and the sciatic, common peroneal, posterior tibial, femoral, saphenous, lateral femoral cutaneous, obturator, ilioinguinal or genitofemoral nerve in the lower extremity. These entrapment syndromes are described more fully under the names of the nerves or of the entrapment neuropathy (e.g. carpal tunnel syndrome, Kiloh Nevin syndrome, tardy ulnar palsy, Mortons metatarsalgia). MR imaging is especially helpful in providing diagnostic information and may delineate a specific and sometimes treatable cause of the compression neuropathy.
Plexus neuropathies result from tumours, infections, trauma, surgical and diagnostic procedures, cervical ribs, and injection. All or some of the branches of the brachial plexus may be involved, leading to the thoracic outlet, scalenus anticus and costoclavicular syndromes, as well as other syndromes.
Hereditary neuropathies represent slowly progressive peripheral neuropathies that are hereditary and can be distinguished according to the specific type of neurons affected (sensory neurons, motor neurons and autonomic neurons). These disorders differ in their mode of inheritance, age of onset, natural history and prognosis, distribution of abnormalities, and pathologic alterations. Some of these disorders lead to neuropathic osteoarthropathy.
In leprosy neuropathy results from sensory or motor impairment with secondary infections. Involvement is most common in the hands, wrists, ankles and feet.
Compression neuropathy includes, in addition to the entrapment neuropathies, compression of the spinal cord with long tract signs in some patients with acromegaly.
DR/RB
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AP radiograph of the foot demonstrates a Lisfranc's fracture-dislocation owing to neuropathic osteoarthropathy in a diabetic patient. Note the lateral subluxation of the second through fifth metatarsals, osseous fragmentation adjacent to the tarsometatarsal joints, and extensive periosteal reaction involving the metatarsal bones.
(Courtesy of Michael Recht, MD, Cleveland, Ohio)
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Neuropathy, Fig.1 | |