Isolated Spinal Intramedullary Neurocysticercosis

Case Report and Review of Literature

Abstract

Cysticercosis is the most common parasitic disease of the central nervous system but an isolated spinal intramedullary involvement is very rare. We present one such case of a 68-year-old female who had spastic paraplegia with bladder involvement. Magnetic resonance imaging (MRI) revealed D3 intramedullary space-occupying lesion. She was treated with surgical excision and her diagnosis was confirmed to be cysticercosis by histopathological examination. With appropriate post-operative rehabilitation and medical management, she was found to have significant recovery. At final follow-up, she was walking with aid and regained her bladder control. A high index of suspicion is required in endemic zones, like India, when the MRI shows an unusual picture of space-occupying intramedullary lesions. With early diagnosis and initiation of treatment, neurocysticercosis (NCC) shows better prognosis than what was previously known.

INTRODUCTION

The most commonly found parasitic disease of the central nervous system is cysticercosis, which is caused by the larvae of the tapeworm.[¹] This disease is endemic in South America, Central America, Mexico, parts of Africa and Asia, and particularly the Indian subcontinent. It accounts for more than 50,000 deaths annually in these regions of the world.[²]

After the ingestion of Taenia solium (pork tapeworm) eggs by humans, the embryos (oncospheres) deposit themselves randomly. The most commonly involved site is the brain (60–92%) followed by subcutaneous tissue (17.8%), skeletal or heart muscle (8.5%), and the eye (5.1%).[³]

Even in endemic areas, spinal cysticercal involvement is rare (0.7–5.85%). Most of the spinal cysticercosis patients have concomitant cerebral involvement.[⁴] On anatomic basis, cysticercosis is classified into extraspinal (vertebral) or intraspinal (epidural, subdural, arachnoid, or intramedullary) diseases. Around 80% of the intraspinal lesion consists of the intradural extramedullary type.[⁵] A patient presenting with isolated intramedullary lesion without concurrent infection elsewhere is extremely rare. Only about 60 cases have been reported to date in literature.[⁶] In this manuscript, we report a similar case of isolated intradural intramedullary neurocysticercosis (NCC).

CASE DESCRIPTION

A 68-year-old female with known hypertension was admitted with a history of weakness, reduced sensation of lower limbs for the past 3 months, and inability to walk for 2 months. She also had urinary retention for the past 20 days. Initially, she developed weakness and severe tightness of lower limbs, which had progressed leading to her being bed bound for 2 months. Examination on presentation showed that she had MRC grade 0/5 power in both lower limbs, reduced sensations below D4 dermatome with reduced perianal sensations, severe spasticity of MAS grade 2, exaggerated deep tendon reflexes with patellar and ankle clonus present, and bilateral Babinski showed extensor response. She had an indwelling Foley catheter at presentation. She was initially admitted under the Department of Neuromedicine and worked up. A magnetic resonance imaging (MRI) (plain with contrast) of the dorsal spine with screening of the whole spine showed a focal intramedullary lesion at D3, which was oval in shape having a diameter of 1.5 cm, with a hypointense wall, and a hyperintense center on T2. There was diffuse edema from D2 to D8, and post-contrast thin peripheral enhancement of the lesion was noted [Figure 1]. Differential diagnoses of cysticercosis, tuberculoma, hemangioblastoma, and metastasis were considered. Her blood investigations were grossly normal.

Figure 1: Schematic diagram showing pre-operative MRI of T1, T2, and contrast sagittal images and T2 axial images showing focal intramedullary lesion at D3; oval in shape with hypointense center on T1; hypointense wall and a hyperintense center on T2 and peripheral-enhancing lesion in contrast with diffuse edema noted from D2 to D8

As there was a solitary lesion with doubtful clinico-radiological diagnosis and had a significant rapid neurological worsening, the patient was planned for an excisional biopsy. After performing a D2-D3 laminectomy, durotomy a midline myelotomy were done, and a fluid-filled cystic lesion was identified. The cyst was aspirated which revealed yellow-colored serous fluid and the cyst wall was excised. Samples were sent for microbiological and histopathological examination.

Intra- and post-operative period was uneventful, after which she was started on aggressive physiotherapy and was discharged on day four. Histopathology revealed a confirmative diagnosis of cysticercosis with characteristic cysticercal cyst and wall [Figure 2]. MRI of the brain [Figure 3] and blood for cysticercal IgG antibody was performed as part of evaluation for any other foci. Her IgG was negative, and MRI of the brain did not show any CNS lesion, thus confirming it to be an isolated NCC. She was started on anti-cysticercal treatment with oral albendezole 400 mg twice daily for 2 weeks and a short course of oral steroids with dexamethasone 4 mg twice daily, which was tapered and stopped over a course of 9 days. Post-operative MRI of the dorsal spine with contrast showed diffuse cord edema at the D2-D3 level, but no enhancing lesion was noted [Figure 4]. At 4 months of final follow-up, the patient had MRC grade 4/5 power, return of sensations in lower limbs, good bladder control, and significantly reduced spasticity. In contrast from bed-bound state at presentation, she was able to walk with support at final follow-up.

Figure 2: Schematic diagram showing microphotograph of intra-operative squash smear showing fragment of cysticercal wall composed of outer acellular pinkish layer, beneath which are tegumental cells with small pyknotic-looking nuclei in a loose fibrillary parenchyma (A). Histopathology of the cysticercal cyst showing the bladder wall thrown into folds (B). Wall is composed of three layers, outer cuticular layer with microvilli, middle cellular layer comprising tegumental cells and inner reticular layer with excretory ducts (C) (magnification: A, C—obj. ×40; B—obj. ×10)

Figure 3: Schematic diagram showing MRI of brain. T1 axial cut showing no evidence of cysticercosis in brain

Figure 4: Schematic diagram showing post-operative T1 and T2 sagittal and axial images which shows no focal lesion and diffuse cord edema from D2 to D3 level, likely due to surgery

DISCUSSION

Humans are intermediate dead-end hosts in cysticercosis, which is a parasitic infection caused by Taenia solium. It continues to be a global problem related to public health, affecting the developing countries more frequently due to socio-cultural and economic factors. In the endemic regions, 3–6% of the population is affected, which globally amounts to 50 million people, with a mortality rate ranging from 6% to 50%.[⁷]

Cysticercal infection occurs after ingestion of tapeworm eggs by humans from undercooked pork and unclean vegetables via faeco-oral route or regurgitation of pre-existing ova from the lower small intestine into the stomach, where embryos (oncospheres) are released following the digestion of shells of ova.[^3,8] After entering circulation, they get deposited in most of the organs and grow into an encysted larval stage termed cysticercus cellulosae. Four stages of NCC were defined by Escobar, namely, vesicular form, which is in the active stage, a transitional stage having colloidal vesicular and granular nodular form, and lastly an inactive stage showing a nodular calcified form.

Cysticercal infestation of the CNS was first described in humans in 1550 by Paranoli. Only in 1856, the first reference about intraspinal cysticercosis was made by Rockitansky.[⁴] Literature shows that NCC affects both sexes equally and is reported in the age group ranging from 20 to 72 years.[⁹] The peak incidence is between 30 and 40 years. Our patient did not fit in the typical age group as she is 62 years old. NCC most commonly affects the brain because it has a 100 times higher blood supply compared to the spine. It typically involves the brain parenchyma, intracranial subarachnoid space, or ventricles. An isolated spinal cysticercosis is rare and is more often not associated with cranial involvement. A spinal lesion may be leptomeningeal, intradural, extramedullary, intramedullary, or epidural. Out of these, leptomeningeal lesions are the commonest, intramedullary are rare, and epidural lesions are extremely rare.[⁶] Our case was confirmed to be an isolated intramedullary NCC after thorough evaluation for other foci.

In NCC, the average survival duration of larvae is five years, with rare reports of the incubation period of even up to 10 years. Duration of exhibiting symptoms before diagnosis has huge variation, with reports ranging from 7 days to 7 years. Even a case with symptoms for ten years before treatment has been reported. In our patient, symptoms were present for a shorter duration of three months only. Spinal NCC occurs most commonly in the thoracic region, similar to our case, followed by cervical, lumbar, and sacral regions. The most common symptom at presentation is motor weakness, followed by pain, sensory deficit, and bladder involvement.[⁹] These symptoms depend on the anatomic location of the cyst and the severity of neural structure compression. Our case had symptoms matching a D3 level intramedullary lesion, which was big enough to cause a mass effect.

As it is rarely encountered in clinical practice, without previous history, suspicion is difficult. High serum eosinophilic count and calcific nodules in soft tissues seen on X-rays are common non-specific findings. An investigation like cerebrospinal fluid (CSF) analysis is helpful, but not diagnostic. CSF analysis in NCC shows variable eosinophilic and lymphocytic pleocytosis, high protein, and low or normal glucose level.[¹⁰] It should be performed with great caution as it can suddenly worsen the neurologic status. The most useful and sensitive investigations for NCC are MRI scan and serological testing. Currently, the most reliable immunological test with 100% specificity is an enzyme-linked immune electrotransfer blot assay of serum and CSF.[¹¹] They not only help in diagnosis but also guide therapeutic management of anti-parasitic treatment. Typical MRI findings of an intramedullary NCC are a cystic lesion, which is hypointense on T1, hyperintense on T2, and a hypointense rim which may be present with surrounding edema in the vesicular stage. Our case had a similar MRI presentation. The closest differential diagnosis is tuberculoma, which shows heterogeneous enhancement post-contrast, unlike NCC, which helps in differentiating it. In the colloidal stage, the cyst appears hyperintense on T1, thus obstructing visualization of the scolex. Peripheral ring enhancement may be present if the cyst is degenerated.[¹¹] The gold standard test for diagnosis of NCC is histopathological examination, which had provided a confirmative diagnosis in our case.

Both surgical and medical management for NCC has been described. Medical management consists of albendazole, which is the preferred drug.[¹²] It is preferred when there is a confirmative diagnosis and when multiple lesions are present making surgery difficult. It is also useful as a pre-operative adjuvant as it is believed to consolidate the cyst and lead to better identification of plane during operative dissection. Albendazole is usually given at a dose of 15 mg/kg/day for 4–6 weeks because cysticercosis mostly is a generalized disease with focal manifestation. In some cases following oral albendazole therapy, further increase in edema and mass effect can be caused, thus worsening the neurology. Those treated with albendazole for >14 days should be monitored for hepatotoxicity and leukopenia. Corticosteroids are used as adjuncts as they reduce inflammation due to larvae and help to increase albendazole blood concentration. As we did not have a confirmatory pre-operative diagnosis, we did not start on any anti-parasitic therapy or corticosteroids. Surgery is crucial when the diagnosis is doubtful and when the patient is neurologically worsening. Laminectomy and excision of the cyst are the preferred surgery method. When pre-operative diagnosis of NCC is suspected, rupture of the cyst intra-operatively should be best avoided. In all cases of intra-operative rupture, high dose of glucocorticoids and vigorous lavage with Ringer’s lactate solution at room temperature are advocated. Surgical outcomes in literature are mixed. Relatively earlier studies like Mohanty et al. in 1997 reported only a 75% satisfactory outcome and Sharma et al. in 1987 reported 60% improvement after surgery, whereas 25% did not improve and 15% died. However, recent studies[^6,9,10,13,14] have shown good surgical outcomes. The American Society for Microbiology Current Consensus Guidelines released in 2002 recommends surgical treatment for intramedullary/extramedullary spinal cysticercosis.[¹⁵] Many studies state that early diagnosis and treatment can improve the outcome. On reviewing the literature, majority (about 50%) of the patients with spinal NCC had a combination of medical and surgical management.[⁹] The prognosis was best when combination therapy was used (78.43%), followed by medical management alone (66.67%) and lastly with surgery alone (42.11%).[⁹] It is postulated that as most of these patients have significant symptoms due to the mass effect of the cyst, combination therapy of surgery and medication helps them the best, similar to what was done for our patient.

CONCLUSION

In summary, despite India being an endemic zone for cysticercosis, presentation as an isolated spinal NCC is still uncommon. It might present with a wide range of symptoms, and careful evaluation of the MRI is needed as it usually points toward the diagnosis. A high index of suspicion is required when the MRI shows an unusual picture of space-occupying intraspinal lesion. When the diagnosis is doubtful, then the immune electrotransfer blot assay of serum is a useful investigation. Multiple lesions in the spine and brain should always be ruled out with necessary imaging. Treatment options include medical and surgical management, but usually both options are used together. In cases with worsening neurology or doubtful diagnosis, surgery remains the preferred treatment option. Most of the recent literature mentions that with early diagnosis and initiation of treatment, NCC usually has a good prognosis than what was previously thought.

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Conflicts of interest

There are no conflicts of interest.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.