Neurocysticercosis (NCC)
The progressive course of this patient's headache, as well as nausea and vomiting, suggested the presence of increased intracranial pressure. A space occupying lesion was foremost in the differential diagnosis. Although there is no pathognomonic headache pattern specific for space-occupying lesions, headaches are typically worse in the morning and disappear after sitting or standing; a finding that was present in this patient. The dramatic worsening of headaches with change of position also suggested intermittent blockage of the ventricular system at the aqueduct of Sylvius or third ventricle. Malignant or benign intracranial tumors, as well as abscesses and cysts, had to be ruled out. This patient was afebrile but fifty percent of patients with brain abscesses can present with an afebrile history. The lack of focal deficits did not exclude space-occupying lesions as the brain is able to accommodate to a slowly growing mass. Headache occurs in 50-60% of patients with primary brain tumors and 35-50% of patients with metastatic tumors. It is not necessarily severe but tends to be persistent and gradually increases in intensity or duration.
Pseudotumor cerebri could present in the same way, and be accompanied by occasional diplopia as was present in this patient. However, she was not overweight and had not been taking any at risk medications. She was not pregnant, hypothyroid, or uremic; still idiopathic pseudotumor cerebri had to be considered in the differential diagnosis until proven otherwise.
Persistence of the headache and nausea and vomiting, with unresponsiveness to pain medications, accompanied by nervousness, can be seen in subacute/chronic meningitis, such as fungal or mycobacterial infections. T.B. meningitis presents as a subacute process. In endemic areas it is usually seen in children or adolescents and develops over several weeks to a few months into a full blown basilar meningitis with cranial nerve palsies. Although this was not the clinical picture of this patient, a subacute/chronic meningitis had to be ruled out. Furthermore, in the course of her disease, she developed symptoms in the proximal extremities suggestive of meningeal irritation or compromise of the upper posterior cervical cord. Herpes zoster infection in the past is unlikely to have explained this symptomatology, since CNS involvement with herpes zoster is more likely to present with panangiitis and ischemia than with signs of increased intracranial pressure.
In order to assess the increased intracranial pressure and possible obstructive hydrocephalus, imaging studies were performed. CT scan and MRI of the head revealed multiple cystic lesions in the basilar cisterns. A supracerebellar cyst appeared to press on the aqueduct of Sylvius, causing obstructive hydrocephalus with enlargement of the third and lateral ventricles.
Cystic lesions in the basilar cisterns may be due to cysticercosis, colloidal cysts, arachnoid cysts, cholesterol cysts, and pyogenic or T.B. abscesses.
Because of the potential pressure gradient at the level of the aqueduct, a lumbar puncture was not done at the time of admission. With worsening of her symptoms soon after the admission, the patient was transferred to neurosurgery for ventriculo-peritoneal shunt placement and decompression.
During the procedure, 15 cc of CSF was drained, with a protein of 89, glucose of 71, and 10 WBCs with 20% eosinophils, 5% neutrophils, 37% monocytes, 20% lymphocytes, and 18% macrophages, with 17500 RBCs. The CSF was negative for RPR, cryptococcus, fungi, and AFB, by serology, smear and culture.
The patient had progressive improvement of the headache and visual symptoms following the shunt placement. A diagnosis of neurocysticercosis was made based on the clinical and radiologic findings, and the patient was started on praziquantel 50 mg/kg, by mouth for two weeks, along with a short course of prednisone therapy. A lumbar puncture a week after surgery and drug therapy showed a clear CSF with opening pressure of 190 mm, protein of 243, glucose of 27 and 153 WBCs with 50% lymphocytes, 22% eosinophils, and 4 RBCs.
Later, cysticercosis immunoblot assay performed at the Center for Disease Control (CDC), was reported positive in both serum and CSF. This test confirmed the diagnosis. Follow-up visit in the clinic, one month later, revealed resolution of the papilledema and headaches.
Under normal conditions, Tenia solium tapeworm is found only in the human intestine (definitive host). The head (scolex) attaches to the intestinal mucosa. The distal segments (proglottids) of the tapeworm mature and become filled with eggs. The eggs are ingested by their natural intermediate host, the pig. They mature into larvae (cysticerci) in pig interstitial tissues. Cysticercus is an oval shaped vesicle, filled with fluid (0.2-2 cm) with an invaginated scolex.[1]
Man becomes the definitive host of the parasite after ingesting the larvae in undercooked pork. However man can also become the intermediate host by ingestion of ova in contaminated food or by autoinfection by the oral-fecal route or reverse peristalsis.[1]
Neurocysticercosis (NCC) occurs when cysticercus penetrates through the blood brain barrier into the CNS.[1]
Cysticercosis is the most common parasitic disease of the CNS.[2] The CNS is involved in 50-70% of all cases. About 50 million people are infected world-wide by neurocysticercosis and each year 50,000 die from the disease.[3] Because of the increasing immigration from endemic areas, NCC is now considered to be an important disease in the southern United States.[4-6] Studies have found a prevalence of cysticercosis in rural areas of Mexico and Ecuador between 1-25 percent. Human NCC is a serious problem in Latin America. A recent review of more than 20,000 autopsies at "The General Hospital of Mexico" (1953-1984) revealed a NCC prevalence rate of 2.38 percent in the general population.[7]
Cysts measure 0.2-2 cm in diameter and are thin-walled. They may induce different degrees of inflammatory reactions in brain tissues, ranging from negligible to exudative or granulomatous lesions. In early inflammatory lesions, the infiltrates include multifocal groups of lymphocytes, plasma cells, and eosinophils located in a fibrous connective tissue capsule surrounding the parasite. Finally, epitheliod and multinucleated giant cells appear, which persist until the complete calcification of the parasites.[8] Parenchymal cysts can be single or multiple; the miliary form with hundreds of cysticerci is most common in children. Cysticerci lodged in the basal cisterns are usually of the racemose type, which is a very large, membranous, grape-like cluster of cysts or a large cyst with multiple septations. The racemose type usually lacks scolices.[1]
Humoral immune response to cysticercosis can be measured in serum, and in cases of NCC quite often in CSF. Studies have shown that most seropositive patients have antibodies to several antigenic components.[10] Grogl discovered 31 antigenic polypeptides in some patients sera by immunoblot.[11] Still there are patients with definite NCC who do not have demonstrable titers of antibody. These patients often have calcified cysts or one or a few viable cysts in early infections.[12] Severe cases of NCC are nearly always serum and CSF positive.[13,14]
The clinical presentation of NCC is determined by the location of cysticerci and the degree of inflammatory response.[9] Most viable cysts induce little or no inflammatory infiltrate, and symptoms appear several years later. In one study this time interval was 4.8 years.[15] Seizures are the most common clinical presentation occurring in 30-92% of patients with parenchymal cysts, which may also induce headaches.[9,16] Cysts may also be asymptomatic.
When lodged in the ventricular system, cysts may be entrapped in the aqueduct or the ventricles, most commonly the fourth ventricle. The clinical manifestations are the result of obstruction of CSF circulation, giving rise to hydrocephalus and resulting in headaches. Papilledema and mental disturbances are also common in patients with hydrocephalus. Meningeal cysts induce a chronic CSF pleocytosis.
Cysticerci located in the subarachnoid space frequently cause inflammatory infiltrates, which give a clinical picture of chronic basal meningitis. NCC may also induce angiitis with resultant ischemia.[17-21] A migraine like presentation of headache and visual symptoms may be seen with occipital lesions. The spinal form of NCC can present like myeloradiculitic syndromes mimicking TB spinal meningitis.
NCC should be suspected in patients coming from endemic areas with persistent headaches or seizures, particularly in young adults.[22] When there is increased intracranial pressure, CT is the most useful initial study and usually diagnostic.[9,23] The pathologic changes of parenchymal NCC have been classified into four stages: vesicular, vesicular colloidal, granular nodular, and nodular calcified.
The racemose form with grape-like clusters of cysts or very large cysts with multiple septations occurs when parasites lodge in the subarachnoid space or within the ventricles. Subarachnoid lesions are difficult to detect on routine CT examination. Evidence for subarachnoid lesions includes distortion or enlargement of cisterns and fissures as well as enhancement of these spaces. MR with its superior resolution can better detect lesions in subarachnoid spaces and within the ventricles.[29]
CSF analysis shows lymphocytic pleocytosis and increased protein in most cases with eosinophilia in 50% of cases and decreased glucose in 25% of cases.[24] Tsang, et al. used immunoblot assays on 532 serum and 46 CSF samples from 148 biopsy proven cases of cysticercosis; all but three were positive. Among the control group there was not a single positive report.[25] Additional data from Wilson, et al. confirmed these data, especially in patients with two or more cysts, but the test was less sensitive in detecting those with a single or calcified cyst. Test sensitivity was higher for serum samples than for CSF specimens.[26]
Seizures must be controlled with AED's without delay. Since most forms of the disease are self limiting, drug therapy of NCC is still controversial. In the encephalitic or disseminated forms, cysticidal therapy must be used with great caution for fear of the effects of accelerated brain inflammation. Drug therapy is less effective for chronic arachnoiditis. NCC is treated with praziquantel for 15-30 days. About 2-3 days after treatment, a strong inflammatory reaction may be initiated with increased protein and cells in the CSF, edema around the lesions, and worsening of symptoms such as headache. This process lasts for 2-3 days, but can be suppressed with steroids. Clinical improvement is seen 2-3 months after treatment. Albendazole given for eight days has also been used as treatment. However, it usually is not used in combination with steroids because steroids may decrease the effectiveness of the drug.[27]
Hydrocephalus may require shunt placement to decrease intracranial pressure or removal of the obstructing cysticercus. Spilling of cyst contents can cause severe meningeal inflammation. Extraparenchymal lesions as well as calcified cysts do not respond well to drug therapy.[9] Niclosamide can be used in cases of auto-infection. Prevention of NCC depends on general, personal, food and meat hygiene. Deep freezing of raw pork for three days at -18 degrees C may have a cysticidal effect.[28]
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