Are Allodynia And Multiple Sclerosis Related

Neuropathy Syndromes

Disturbances of the peripheral nervous system may be subdivided into those affecting neuronal cell bodies (neuronopathy) and those affecting peripheral nerve processes (peripheral neuropathy). Neuronopathies include anterior horn cell syndromes (motor neuron lesions; p. 50) and sensory neuron syndromes (sensory neuronopathy, ganglionopathy; pp.2, 107, 390). Motor neuron diseases are described on p. 304. Peripheral neuropathy is characterized by damage to myelin sheaths (myelinopathy) and/or axons (axonopathy). Neuropathies may affect a single nerve (mononeuropathy), multiple isolated nerves (mononeuropathy multiplex), all peripheral nerves generally (polyneuropathy), or all peripheral nerves generally with accentuation of one or a few (focal polyneuropathy). Polyneuropathy may be accompanied by autonomic dysfunction (p. 140). The terms poly-neuropathy (PNP) and peripheral neuropathy are often used synonymously. Radiculopathies (nerve root lesions) are classified as either mon-oradiculopathies or polyradiculopathies, depending on whether a single or multiple roots are involved.

■ Symptoms and Signs

Peripheral neuropathy causes sensory, motor, and/or autonomic dysfunction. Its etiological diagnosis is based on the pattern and timing of clinical manifestations (Table 53, p. 390). Sensory dysfunction (p. 106) is often the first sign of neuropathy. Sensory deficits have distinctive patterns of distribution: they may be predominantly proximal or distal, symmetrical (stocking/glove distribution) or asymmetrical (multiple mononeuropathy), or restricted to individual nerves (cranial nerves, single nerves of the trunk or limbs; p. 32 f). Disordered sensory processing (p. 108 f) can produce hyperalgesia (more pain than normal upon noxious stimulation), hyperesthesia (increased tactile sensation with lowering of threshold), paresthesia (spontaneous or provoked abnormal sensation), dys-esthesia (spontaneous or provoked, abnormal, painful sensation), or allodynia (pain resulting from nonnoxious stimuli). Damage to rapidly conducting, thickly myelinated A-f> fibers causes paresthesiae such as tingling, prickling ("pins and needles"), formication, and sensations of tension, pressure, and swelling. Damage to slowly conducting, thinly myelinated A-S and C fibers (small fiber neuropathy) causes hypalgesia or analgesia with thermal hypesthesia or anesthesia, abnormal thermal sensations (cold, heat), and pain (burning, cutting, or dull, pulling pain).

Motor dysfunction (p. 50). Weakness usually appears first in distal muscles. In very slowly progressive neuropathies, muscles may become atrophic before they become weak, but weakness is usually the initial symptom, accompanied by hyporeflexia or areflexia. The cranial nerves can be affected. Hyperactivity in motor A-a fibers produces muscle spasms, fascicula-tions, and/or myokymia.

Autonomic dysfunction (p. 146 f) can be manifest as vasomotor disturbances (syncope), cardiac arrhythmias (tachycardia, bradycardia, fixed heart rate), urinary and gastrointestinal dysfunction (urinary retention, diarrhea, constipation, gastroparesis), sexual dysfunction (impotence, retrograde ejaculation), hyperhidrosis or hypohidrosis, pupillary dysfunction, and trophic lesions (skin ulcers, bone and joint changes).

Polyneuropathies can be hereditary or acquired (see Table 54).

The diagnosis of a neuropathy is based on the characteristic clinical findings and patient history. Additional diagnostic studies not indicated on the basis of the patient history and clinical findings may produce not only unjustified costs but also confounding data, leading occasionally to misdiagnosis. Studies to be performed as indicated include neurophysiological tests (nerve conduction studies, electromyography), laboratory tests (blood, CSF), tissue biopsy (nerve, skin, muscle), and genetic tests.

• Neuronopathy

• Radiculopathy

• Axonopathy

• Myelinopathy

• Disorder of neuromuscular conduction

Efferent myelinated nerve

Motor end plate

Cutaneous receptors

Spinal ganglion

Motor neuron

Efferent myelinated nerve

Motor end plate

Neuronopathy

Motor neuron

Cutaneous receptors

Spinal ganglion

Spinal Cord Modules
Spinal cord

Autonomic ganglion Unmyelinated (autonomic) nerve v

Spinal/peripheral nerve

Peripheral nerve lesions (1

Asymmetrical

Proximal symmetrical

Peripheral nerve lesions (1

Asymmetrical

Proximal symmetrical

Neuropathies

Hereditary neuropathies

Acquired neuropathies

Hereditary neuropathies

Acquired neuropathies

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