InheritedCharcot-Marie-Toothneuropathy,type1,typeII,andX-linkedHereditaryneuropathywithliabilitytopressurepalsy
OthersParaneoplastic,someleukodystrophies http://ebooksmedicine.net
Guillain-Barré syndrome is a rapidly progressive acute demyelinating disorder affecting motor axons, resulting in ascending weakness that can lead to death from failure of respiratory muscles within days of onset of symptoms. It is one of the most common life-threatening diseases of the peripheral nervous system. Guillain-Barré syndrome appears to be triggered by an infection or vaccination that breaks down self-tolerance, thereby leading to an autoimmune response. Associated infectious agents include Campylobacter jejuni, Epstein-Barr virus, cytomegalovirus, human immunodeficiency virus (HIV), and, most recently Zika virus. The injury is most extensive in the nerve roots and proximal nerve segments and is associated with mononuclear cell infiltrates rich in macrophages. Both humoral and cellular immune responses are believed to play a role in the disease process. Treatments include plasmapheresis (to remove offending antibodies), intravenous immunoglobulin infusions (which suppress immune responses through unclear mechanisms), and supportive care, such as ventilatory support. Patients who survive the initial acute phase of the disease usually recover with time.
CIDP is the most common chronic acquired inflammatory peripheral neuropathy, characterized by symmetrical mixed sensorimotor polyneuropathy that persists for 2 months or more. Both motor and sensory abnormalities are common, such as weakness, difficulty in walking, numbness, and pain or tingling sensations. Like Guillain-Barré syndrome, CIDP is immune mediated. But in contrast to Guillain-Barré syndrome, CIDP follows a chronic, relapsing-remitting, or progressive course. It occurs with increased frequency in patients with other immune disorders, such as systemic lupus erythematosus and HIV infection. The peripheral nerves show segments of demyelination and remyelination (
Fig. 22.2A ). In long-standing cases, repeated activation and proliferation of Schwann cells with episodes of regeneration result in the concentric arrangement of multiple Schwann cells around individual axons to produce multilayered structures likened to onion bulbs. Treatment includes plasmapheresis and administration of immunosuppressive agents. Some patients recover completely, but more often recurrent bouts of symptomatic disease lead to permanent loss of nerve function.
Diabetes is the most common cause of peripheral neuropathy, usually developing with long-standing disease. Diabetic neuropathies include several forms that can occur singly or together.
Autonomic neuropathy is characterized by changes in bowel, bladder, cardiac, or sexual function.
Lumbosacral radiculopathy usually manifests with asymmetric pain that can progress to lower extremity weakness and muscle atrophy.
Distal symmetric sensorimotor polyneuropathy is the most common form of diabetic neuropathy. Sensory axons are more severely affected than motor axons, resulting in a clinical presentation dominated by paresthesias and numbness. This form of diabetic polyneuropathy results from the length-dependent degeneration of peripheral nerves and does not neatly fit into the axonal or demyelinating category but instead often exhibits features of both. The pathogenesis of diabetic neuropathy is complex; accumulation of advanced glycosylation end products resulting from hyperglycemia, increased levels of reactive oxygen species, microvascular changes, and changes in axonal metabolism, all have been implicated. Strict glycemic control is the best form of therapy.
Toxic,Vasculitic, and Inherited Forms of Peripheral Neuropathy
There are diverse other causes of peripherlal neuropathy (
Table 22.1 ), some of which merit brief discussion.