Volume 4, Case 1
Soledad Ureta Raroque, M.D.
Children's Medical Center of Dallas
University of Texas Southwestern School of Medicine
This is a five year old Latin American female who presented to the emergency department (ED) after having a presumed seizure. She was playing in the school yard when she suddenly lost consciousness and developed generalized tonic-clonic movements of the upper and lower extremities for approximately five minutes. EMS was called and she was brought to the ED in a post-ictal state. In the ED, she was noted to develop a two-minute episode of right sided tonic-clonic movements of the upper and lower extremities with eyes deviating to the left. She was incontinent of urine. There were no associated symptoms of fever, cough, or upper respiratory illness.
Past medical history was significant for an appendectomy six months prior because of abdominal pain. The pathology report described a slightly inflamed appendix with the incidental finding of enterobius vermicularis within the lumen of the appendix. She also had a subsequent emergency department visit for abdominal pain and fever. Her work-up included a complete blood count, electrolytes, urinalysis, and abdominal films. She was subsequently discharged with a diagnosis of benign abdominal pain and fever, probably due to a viral syndrome. Her travel history included a trip to Mexico earlier in the year.
Exam: VS T37.6C, HR 110, RR 30, BP 128/62. The patient appeared sleepy but arousable and responded appropriately to family members. Her pupils were equal and reactive. Both tympanic membranes had good light reflexes, and her neck was supple. Her breath sounds were clear and equal. She had a regular heart rate and rhythm with no murmurs. Peripheral pulses were brisk, with good capillary refill. The abdomen was soft and non-tender with normal bowel sounds. There was an appendectomy scar on the right lower quadrant. No neurological deficits could be detected. She had no clonus. Her reflexes were normal.
Because of the presentation of a focal seizure, a CT scan of the head was obtained.
View Head CT image.
A high cut is shown here. The image on the left is without contrast. The view on the right is obtained after IV contrast is administered. This CT scan shows a small intraparenchymal ring-enhancing lesion in the left parietal lobe near the vertex, with a fair amount of surrounding edema consistent with neurocysticercosis. There is no mass effect on the ipsilateral ventricular system, no hemorrhage, and no extra-axial fluid collection. This appearance is not specific, as a brain abscess, tumor, or other lesions may also have this appearance.
She was hospitalized overnight and started on oral carbamazepine. Electroencephalography was abnormal, showing diffuse slowing, which was greater in the left hemisphere. Her eye exam showed no evidence of cysticercosis. She was not treated with anti-cysticercal drugs but was continued on oral carbamazepine. She has subsequently remained seizure-free.
Teaching Points:
1. Onset of a focal, non-febrile seizure, which subsequently generalizes, suggests a focal CNS lesion. The use of imaging studies, CT scan in particular, is warranted to rule out a mass lesion or a bleed which could be life threatening.
2. Cysticercosis is the most common parasitic infection of the human central nervous system, mainly occurring in developing countries. The increasing number of immigrants from endemic areas in Latin America, Asia and Africa has resulted in a higher prevalence of neurocysticercosis in the United States. Neurocysticercosis affects males and females of all ages, with a peak incidence between 30 and 50 years of age. Sixty to ninety percent of patients with cysticercosis have CNS lesions.
3. Poorly cooked or raw pork is the only source of human infection for the development of the adult worm (Tinea solium). Human infection with cysticerci can involve thousands of organisms obtained from various sources: ingestion of T. solium eggs in contaminated food or water; self-infection from the presence of the adult worm in the intestine; and possibly internal autoinfection, in which the eggs come in contact with the stomach acid, thus possibly allowing hatching and penetration of the larvae into the tissues. Stools of the patient and the immediate family should be examined for ova and proglottid of T. solium and treated accordingly. Prevention involves awareness of the infection route and the use of good sanitary and personal hygiene measures.
4. The presence of the adult worm in the GI tract usually causes no problems other than slight irritation at the site of attachment or vague abdominal symptoms (hunger pains, indigestion, diarrhea, and/or constipation). There may be a low-grade eosinophilia, usually under 15%. This patient initially presented with several episodes of abdominal pain, which on one occasion led to the removal of the appendix. Parasitic infections may certainly present as abdominal pain, and further studies on the stool (ova and parasites) may reveal other ongoing infestations.
5. The brain parenchyma is the most common location for neurocysticercosis, followed by the ventricles and subarachnoid spaces. The cysts may be located anywhere in the brain, most commonly in the cerebral gray matter, followed by the brain stem, cerebellum, and spinal cord. When the cysticercus dies, it sets up an antigenic stimulus resulting in a local inflammatory process and breakdown of the blood-brain barrier; as a consequence, contrast enhancement is seen. The completely calcified lesions of cysticercosis represent the dead cysticercus larvae and do not enhance or elicit edema. It is estimated that it takes 4-7 years for the dead larvae to calcify, which may explain why calcification is much less commonly seen in the pediatric age group than in adult patients with cysticercosis. The differences between adults and children with cysticercosis include: (1) calcifications being more commonly seen in adults, and (2) diffusely homogeneous enhancing lesions being more commonly seen in children. Hydrocephalus may also develop in 25% of patients with neurocysticercosis secondary to obstruction of CSF outflow or cysts in the basal cisterns. Occasionally, the parasite may lodge in the eye, most commonly under the retina in the posterior pole, often over the macular area. The inflammatory reaction that ensues may lead to visual loss.
6. It may be difficult to confirm the diagnosis, even using CT or MRI techniques. Serologic testing can be helpful; however, there may be cross-reactivity between cysticercosis and other parasitic infections. The enzyme-linked immunotransfer blot assay to detect antibody to T. solium, for serum and cerebrospinal fluid, is the antibody test of choice. It is available through the Centers for Disease Control and Prevention. The antibody assays, however, are rarely positive in children with solitary parenchymal lesions, but are often positive in those with inflamed lesions in contact with the subarachnoid space.
7. The CSF in neurocysticercosis is abnormal in about fifty percent of cases. The most common finding is a lymphocytic pleocytosis (>10 wbc/cu mm). The presence of eosinophils (detected by Wright's stain) in the CSF is rare and increases the probability of the diagnosis. It is seen in fifteen percent of cases of neurocysticercosis. Other laboratory findings in the CSF that may be associated with neurocysticercosis include elevated opening pressure in 40% of cases, elevated protein in 40%, and low glucose in 25% of cases (2).
8. Therapy for the different forms of neurocysticercosis must be individualized according to the level of disease activity, the number of lesions, the location of the parasite and the presence or absence of inflammation as determined by CT or MRI of the brain. Patients with active disease or with multiple uninflamed cysts can be treated with praziquantel at 50 mg/kg/day in three divided doses for 15 days. The use of corticosteroids is recommended for two to three days before and during drug therapy to minimize the strong inflammatory reaction of the host to acute destruction of parasites in the brain. They may however reduce the effectiveness of the anti-cysticercal drug. Another drug, albendazole, appears to have the same efficacy as praziquantel but is not yet approved by the FDA. The drug is usually given at an oral dose of 15 mg/kg/day in three divided doses for 28 days; however, shorter courses for 3-8 days also appear effective. Intraocular or ventricular cysts may require surgical resection.
9. Patients with inactive disease or calcification alone do not need anti-cysticercal therapy since these lesions represent previous cysts destroyed by the host's immune reaction. Treatment with antiepileptic drugs, such as carbamazepine and/or phenytoin, is advised when calcifications are associated with seizures. Seizures may recur for months and will require anticonvulsant medication until patients have been seizure-free for 1 to 2 years.
References