1. Signs and symptoms of excessive catecholamine (VMA/HVA) secretion: Intermittent attacks of sweating, flushing, pallor, headaches, palpitation, and hypertension. Hypertension is usually renin induced due to renovascular compromise and is seen in 1-5% of patients. Normal levels of VMA and HVA are listed in Table A1-29.

2. Signs and symptoms of vasoactive intestinal peptide (VIP) secretion: Intractable watery diarrhea resulting in failure to thrive, associated with abdominal dis-tention and hypokalemia due to the secretion of an enterohormone, VIP, by the neuroblastoma cells (Kerner-Morrison syndrome). Most of the VIP-secreting tumors are mature histologically (ganglioneuroblastoma or ganglioneuroma) and have favorable outcome.

3. Acute myoclonic encephalopathy: The syndrome of opsoclonus and myoclonus (OM) consists of:

a. Bursts of rapid involuntary random eye movements in all directions of gaze (opsoclonus)

b. Motor incoordination due to frequent, irregular jerking of muscles of the limbs and trunk (myoclonic jerking)

c. Symptoms may or may not resolve after the tumor is removed or symptoms may resolve only after several months. In some cases these symptoms are permanent.

d. Prognosis for survival is favorable because tumor usually displays favorable biological features. If tumor displays biologically unfavorable features the prognosis is unfavorable.

All children presenting with OM should be evaluated for the presence of neuroblastoma (because more than 30% of them have an occult tumor of neural crest origin). Meta-iodobenzylguanidine (MIBG) scan, octreoid (somatostatin receptor) scan, CAT scan of the neck, chest, abdomen, and pelvis, and urinary Vanillyl mandelic Acid (VMA), and Homovanillic Acid (HVA) measurement may help detect the presence of neuroblastoma.

Pathophysiology of OM

This syndrome is not due to direct involvement of the central nervous system (CNS) by tumor or due to the production of catecholamines. It is associated with well-defined IgG and IgM autoantibodies that bind to the cytoplasm of cerebellar Purkinje cells and to some axons in the white matter. They also bind to the large and small axons of the peripheral nerves. Western blot analysis shows a distinctive pattern of binding to several neural proteins of the neurofilaments. The role of these autoantibodies in the pathogenesis of OM is unclear at the present time. Diffuse and extensive lymphocytic infiltration with lymphoid follicles is a characteristic histologic feature of OM. This observation suggests an immune-mediated mechanism for this rare syndrome.

Treatment of OM

• If dexamethasone fails, high-dose Intravenous Immunoglobulin (IVIG) 150-500 mg/kg/day for 4-5 days. It may also provide a steroid-sparing effect.

Chemotherapy: Children who receive chemotherapy, due to their advanced stages, have a better neurologic outcome of OM than patients who do not receive chemotherapy.

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