Chapter 097. Paraneoplastic Neurologic Syndromes (Part 9)

Vasculitis of the nerve and muscle causes a painful symmetric or asymmetric distal sensorimotor neuropathy with variable proximal weakness. It predominantly affects elderly men and is associated with an elevated erythrocyte sedimentation rate and increased CSF protein concentration. SCLC and lymphoma are the primary tumors involved. Pathology demonstrates axonal degeneration and T cell infiltrates involving the small vessels of the nerve and muscle. Immunosuppressants (glucocorticoids and cyclophosphamide) often result in neurologic improvement.Peripheral nerve hyperexcitability (neuromyotonia, or Isaacs syndrome) is characterized by spontaneous and continuous muscle fiber activity of peripheral nerve origin. ...
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Chapter 097. Paraneoplastic Neurologic Syndromes (Part 9) Chapter 097. Paraneoplastic Neurologic Syndromes (Part 9) Vasculitis of the nerve and muscle causes a painful symmetric orasymmetric distal sensorimotor neuropathy with variable proximal weakness. Itpredominantly affects elderly men and is associated with an elevated erythrocytesedimentation rate and increased CSF protein concentration. SCLC and lymphomaare the primary tumors involved. Pathology demonstrates axonal degeneration andT cell infiltrates involving the small vessels of the nerve and muscle.Immunosuppressants (glucocorticoids and cyclophosphamide) often result inneurologic improvement. Peripheral nerve hyperexcitability (neuromyotonia, or Isaacs syndrome) ischaracterized by spontaneous and continuous muscle fiber activity of peripheralnerve origin. Clinical features include cramps, muscle twitching (fasciculations ormyokymia), stiffness, delayed muscle relaxation (pseudomyotonia), andspontaneous or evoked carpal or pedal spasms. The involved muscles may behypertrophic, and some patients develop paresthesias and hyperhydrosis. CNSdysfunction, including mood changes, sleep disorder, or hallucinations, may occur.The electromyogram (EMG) shows fibrillations; fasciculations; and doublet,triplet, or multiplet single unit (myokymic) discharges that have a high intraburstfrequency. An immune pathogenesis is suggested by the frequent presence ofserum antibodies to VGKC. The disorder often occurs without cancer; ifparaneoplastic, benign and malignant thymomas and SCLC are the usual tumors.Phenytoin, carbamazepine, and plasma exchange improve symptoms. Paraneoplastic autonomic neuropathy usually develops as a component ofother disorders, such as LEMS and encephalomyelitis. It may rarely occur as apure or predominantly autonomic neuropathy with adrenergic or cholinergicdysfunction at the pre- or postganglionic levels. Patients can develop several life-threatening complications, such as gastrointestinal paresis with pseudoobstruction,cardiac dysrhythmias, and postural hypotension. Other symptoms include drymouth, erectile dysfunction, anhidrosis, and sphincter dysfunction; abnormalpupillary responses may be found. The disorder has been reported to occur inassociation with several tumors, including SCLC, cancer of the pancreas or testis,carcinoid tumors, and lymphoma. Because autonomic symptoms can also be thepresenting feature of encephalomyelitis, serum anti-Hu and anti-CV2/CRMP5antibodies should also be sought. Serum antibodies to ganglionic acetylcholinereceptors have been reported in this syndrome, but they also occur without acancer association. (See Chap. 370.) Lambert-Eaton Myasthenic Syndrome LEMS is discussed in Chap. 381. Myasthenia Gravis Myasthenia gravis is discussed in Chap. 381 Polymyositis-Dermatomyositis Polymyositis and dermatomyositis are discussed in detail in Chap. 383 Acute Necrotizing Myopathy Patients with this syndrome develop myalgias and rapid progression ofweakness involving the extremities and the pharyngeal and respiratory muscles,often resulting in death. Serum muscle enzymes are elevated, and muscle biopsyshows extensive necrosis with minimal or absent inflammation and sometimesdeposits of complement. The disorder occurs as a paraneoplastic manifestation ofa variety of cancers including SCLC and cancer of the gastrointestinal tract, breast,kidney, and prostate, among others. Glucocorticoids or treatment of the underlyingtumor rarely control the disorder. Paraneoplastic Visual Syndromes This group of disorders involves the retina and, less frequently, the uveaand optic nerves. The term cancer-associated retinopathy is used to describeparaneoplastic cone and rod dysfunction characterized by photosensitivity,progressive loss of vision and color perception, central or ring scotomas, nightblindness, and attenuation of photopic and scotopic responses in theelectroretinogram (ERG). The most commonly associated tumor is SCLC.Melanoma-associated retinopathy affects patients with metastatic cutaneousmelanoma. Patients develop the acute onset of night blindness and shimmering,flickering, or pulsating photopsias that often progress to visual loss. The ERGdemonstrates reduction in the b-wave amplitude. Paraneoplastic optic neuritis anduveitis are very uncommon and can develop in association with encephalomyelitis.Some patients with paraneoplastic uveitis harbor anti-CV2/CRMP5 antibodies. Some paraneoplastic retinopathies are associated with serum antibodies thatspecifically react with the subset of retinal cells undergoing degeneration,supporting an immune-mediated pathogenesis (Tables 97-2 and 9 ...