HISTORY OF PRESENT ILLNESS
A 4-year-old African-American male presented to the emergency department with a 2-day history of fever. He awoke the day prior to admission and complained of neck pain and headache in the back of his head. She also noted that he would crawl down the stairs instead of walking and was unable to put food into his mouth. The mother also reported that he appeared confused. She asked him to bring her a hat and he returned with a book. She states that he has no history of medication ingestions, vomiting, diarrhea, head injury, or rashes. There were no ill contacts.
The boy was born at 32 weeks gestation and had a history of unconjugated hyperbilirubinemia. He had been hospitalized in the neonatal intensive care unit for 2 weeks, but did not require endotracheal intubation or antibiotics. He also had a history of plumbism with a peak lead level of 25 mcg/dL; however, a lead level 2 weeks ago was 10 mcg/dL. He did not take any medication and had no allergies.
T 37.5°C; HR 110 bpm; RR 24/min; BP 100/65 mmHg
Height 50th percentile; Weight 50th percentile
In general, he was a well-appearing boy who was sitting quietly in his mother’s arms. He was appropriately interactive during the examination. He had no nuchal rigidity, tympanic membranes were clear and had normal fundoscopic examination. Cardiac, pulmonary, and abdominal examinations were normal. The cranial nerves were grossly intact. He had brisk reflexes symmetrically with downgoing toes. Tone and strength were normal and symmetric throughout. The child displayed truncal ataxia while sitting and was unable to walk without assistance due to ataxia. He also had dysmetria with finger-nose-finger. A rash suggested the diagnosis (Figure 8-7).
FIGURE 8-7. Patient’s rash.
The complete blood count revealed a WBC count of 7800 cells/mm3 (34% segmented neutrophils, 51% lymphocytes, 10% monocytes, 5% eosinophils), a hemoglobin of 12.2 g/dL, and a platelet count of 275 000/mm3. Electrolytes, urinalysis, PTT, PT, ammonia, and liver function tests were normal. His serum glucose was 84 mg/dL. Head CT was negative. Cerebral spinal fluid revealed 3 WBCs/mm3 and 1 RBC/mm3, with a glucose of 54 mg/dL and protein of 15 mg/dL. There were no bacteria on CSF Gram stain. Lead level was 8 mcg/dL.
COURSE OF ILLNESS
The child was admitted to the hospital and treated empirically with vancomycin, cefotaxime, and acyclovir.
DISCUSSION CASE 8-6
The life-threatening causes of ataxia that must be addressed are acute bacterial meningitis, cerebellar abscess, neoplasm, and metabolic disturbances including hypoglycemia, hyponatremia, and hyperammonemia. Toxin ingestions, particularly alcohol, benzodiazepines, and phenytoin, must also be considered. Posterior fossa tumors and metastatic malignancies may present with ataxia. Guillain-Barré may also present as ataxia with lower extremity weakness in an otherwise healthy child. Infectious causes include bacterial meningitis and Listeria rhombencephalitis. Measles, mumps, and rubella were common precipitants of cerebellar ataxia prior to widespread vaccination. However, the vast majority of children with ataxia will fall into the postinfectious acute cerebellar ataxia. Common inciting agents are enteroviruses, influenza, Epstein-Barr virus, and varicella.
The next day the boy developed a puritic vesicular rash on his face and trunk. The rash consisted of clear fluid-filled vesicles with a surrounding irregular margin of erythema resembling “dewdrops on a rose petal.” Several stages of the rash were present in the same area, a finding consistent with varicella (Figure 8-7). The diagnosis is acute cerebellar ataxia secondary to varicella infection.
INCIDENCE AND EPIDEMIOLOGY
Prior to the availability of the varicella vaccine, approximately 4 million cases of varicella occurred in the United States. Nearly 100 000 hospitalizations and 100 deaths occurred each year in the United States from the infection. Ninety-five percent of the cases occurred in people under the age of 20 years, and nearly half of the deaths occurred in children. However, the vaccine licensed in 1995 has resulted in a marked decrease in severe varicella infection in the United States. The vaccine prevents 70%-85% of mild disease and greater than 95% of severe disease.
Varicella is contagious 24-48 hours prior to the eruption of the rash until all of the vesicles have crusted over. The incubation period is 10-21 days and prodromal symptoms include fever, headache, and malaise. The lesions initially occur on the face and trunk and spread to the extremities. They begin as erythematous macules that evolve to form clear, fluid-filled vesicles with irregular surrounding erythema (Figure 8-7). These vesicles are classically described as “dewdrops on a rose petal.” New lesions erupt as older lesions are crusting. The lesions are typically pruritic.
Varicella is usually benign and a self-limited infection and complications are rare; however, the two most common complications of varicella are secondary bacterial infections and neurologic disturbances. Group A beta-hemolytic Streptococcus and Staphylococcus aureus are the notorious causes of bacterial superinfection. Neurologic manifestations include cerebellar ataxia and meningoencephalitis. Cerebella ataxia is characterized by gait disturbance, nystagmus, and slurred speech. Signs of meningoencephalitis include seizures, altered level of consciousness, and nuchal rigidity. The neurologic sequelae usually develop 3-7 days after the eruption of the rash but, as in this case, may also appear during the incubation phase making the diagnosis difficult if there is no history of varicella exposure. The etiology of the neurologic complications is unknown; however, direct invasion by the virus and an autoimmune response are proposed theories.
A thorough history focused on possible ingestions, trauma, associated symptoms, or viral syndromes is necessary with any child presenting with ataxia. Close attention to vital signs, an altered level of consciousness, or weakness help distinguish between life-threatening and more benign causes of ataxia.
Lumbar puncture. Cerebrospinal fluid examination may be normal or reveal a mild lymphocytic pleocytosis (fewer than 200 WBCs/mm3) and elevated protein (50-200 mg/dL).
Varicella detection. Varicella may be detected in the cerebrospinal fluid and from lesion scrapings by polymerase chain reaction (PCR). The sensitivity and specificity of PCR for detection of varicella in skin lesions are >98%. If PCR is not available, direct fluorescent-antibody staining of epithelial cells from the base of newly formed vesicles detects viral antigens and is a reasonable alternative (sensitivity, ~85%; specificity, ~90%). This rapid test readily differentiates varicella from herpes simplex virus, which can present with similar lesions. Isolation of varicella from tissue culture provides definitive diagnosis but identification requires 3-7 days. Thus, viral culture serves to confirm a diagnosis already made by clinical examination or PCR or rapid antigen testing. Varicella IgM antibody detection should not be used for clinical diagnosis since the test results in many false-positives and false-negatives.
Neuroimaging. MRI should be considered to exclude posterior fossa tumors. Neuroimaging is necessary if there is a history of trauma, focal neurologic examination, or increased intracranial pressure.
Other studies. Testing of serum and urine for toxic ingestions may help narrow the differential diagnosis. Laboratory studies including glucose and serum electrolytes are also appropriate in the evaluation.
Acyclovir is the drug of choice for the treatment of varicella in high-risk patients, including neonates and immunocompromised children. Patients with disseminated varicella disease (e.g., pneumonia, encephalitis) also benefit from intravenous acyclovir. However, acyclovir is not recommended in cases of cerebellar ataxia since it does not alter the course of the illness. Otherwise healthy patients may benefit from acyclovir if the drug is initiated within 24 hours after the appearance of the initial skin lesions; however, this practice is not universally recommended.
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