INTRAMEDULLARY TUBERCULOMA OF THORACIC SPINAL CORD IN AN APPARENTLY HEALTHY NIGERIAN: CASE REPORT

Abstract

Spinal intramedullary is an uncommon form of tuberculosis causing spinal cord injury in this environment. We report a case of thoracic intramedullary tuberculoma in an immunocompetent male Nigerian with negative screening for tuberculosis. He presented with 8 months history of back pain and 2 months history of progressive weakness in both lower limbs. Physical examination revealed a well-nourished man with spastic paraplegia. Chest radiograph and CT scan were normal but Magnetic resonance imaging (MRI) of the thoracolumbar region showed cord oedema and circumscribed intramedullary lesions at D12 and L1 levels with target sign. The patient was promptly prepared and had D12 and L1 laminectomy and posterior myelotomy with excision of the intramedullary lesion. Histology showed granulomatous lesion with central caseation in keeping with a tuberculoma. He was treated with a 4-drug antituberculous regimen with physiotherapy and he made complete neurological recovery 8 months post-operatively.

Intramedullary tuberculoma should be considered in differential diagnosis of intramedullary tumors in this environment. Treatment with antituberculous drugs results in good outcome.

Introduction

Spinal intramedullary tuberculoma (IMT) is an uncommon form of central nervous system (CNS) tuberculosis. A low incidence of 2 in 1000 cases of CNS tuberculosis has been reported and this incidence remains low even in areas with endemic tuberculosis1,2. Most patients have evidence of active tuberculosis in others part of the body and the incidence tends to be higher in immunosuppressed patients. Often diagnosis is made after an incisional biopsy but in the absence of tuberculosis in other systems, the diagnosis is often missed. The thoracic spinal cord is the most affected area of the spine by intramedullary tuberculoma1,3. Magnetic resonance imaging features of the lesion vary depending on the stage of disease.1 Surgery and antituberculous therapy often result in complete neurological recovery1^-4. We report a case of an immunocompetent patient with thoracic paraplegia secondary to intramedullary tuberculoma who was treated surgically along with antituberculous therapy and physiotherapy with complete neurological recovery.

Case Reports

A 45-year-old man presented to our service with low back pain of eight months duration and progressive weakness in both lower limbs of two months duration. He also had associated bi-sphincteric dysfunction. He had no weight loss or any other constitutional symptoms. He had no previous history of tuberculosis or exposure to a patient with tuberculosis and no antecedent history of trauma to the back.

Clinical examination revealed a healthy looking man with intact higher mental functions and normal cranial nerves. The muscle bulk, tone, power and deep tendon reflexes were normal in both upper limbs. Examination of the lower limbs revealed complete paraplegia (power 0/5) with reduced muscle bulk, tone and reflexes. The plantar reflex was extensor bilaterally. There was sensory impairment up to L1 dermatome below which there was tactile allodynia. Otherwise the rest of the clinical examination was normal.

MRI of thoracolumbar spine showed circumscribed lesions at D12 and L1 with target sign and spinal cord expansion around the same region (Figure 1). Plain radiograph and computed tomographic scan of the chest were normal. Hematological investigations were normal with a negative serological screening for HIV 1 and 2. A diagnosis of an intramedullary tumour was made with a remote possibility of a tuberculoma. He underwent D12- L1 laminectomy and posterior myelotomy with excision of a well-circumscribed grayish mass under general endotracheal anesthesia. Histopathology revealed a granulomatous lesion with a central area of caseation in keeping with a tuberculoma (Figure 2).

He was subsequently commenced on intensive phase of antituberculous drugs with once daily doses of isoniazid (300 mg), rifampicin (600 mg), pyrazinamide (1500 mg) and ethambutol (800 mg) which he had for 2 consecutive months. In the continuation phase, he had only rifampicin and isoniazid at the same doses for additional 10 months. He was also commenced on plain carbamazepine at a dose of 200 mg twice daily for the allodynia he had.

After laminectomy and commencement of antituberculous drugs, his bi-sphincteric dysfunction and allodynia resolved while power in the lower limbs gradually returned to normal. By the time he was seen for follow up 8 months after surgery and commencement of antituberculous drugs, he was fully ambulant and has since returned to his job and premorbid activities.

Discussion

According to the Global Burden of Diseases 2013, tuberculosis is still a major public health problem worldwide with an all-form tuberculosis incidence of 7.5 million in HIV-positive and HIV-negative individuals combined5. CNS involvement is seen in up to 10% of patients with tuberculosis6. First reported by Abercrombie in 1828, spinal intramedullary tuberculoma is extremely rare, constituting 2 of 1000 cases of CNS tuberculosis1,2,7. In a series of 29 cases of spinal tuberculosis seen over a period of 20 years, Nassbaum et al reported that only 7% were due to intramedullary tuberculoma8. In spite of a high incidence and prevalence of tuberculosis, there is paucity of information on intramedullary tuberculosis in adults in sub-Saharan Africa.

Intramedullary tuberculoma (IMT) occurs in the young age group with about one-thirds of them not having evidence of tuberculosis elsewhere9,10,11; our patient was 45 years old and did not have any evidence of tuberculosis in any other part of the body. The commonest region affected by spinal intramedullary tuberculoma is the thoracic region, occurring in about 70% of cases3 as was the case in the index patient had a lesion that affects the D12 and L1 regions of the cord. The probable reason why spinal intramedullary tuberculoma involves the thoracic spinal cord predominantly could be because this region receives about 45% of the entire blood supply to the spinal cord12 and it is known that Mycobactrium tuberculosis is an obligate aerobe which thrives best in a region where the partial pressure of oxygen is high. Intramedullary tuberculoma frequently presents with symptoms and signs of sub-acute spinal cord compression including motor, sensory or autonomic manifestations; Brown-Sequard syndrome has also been reported13. MacDonnell et al14 reported spastic and flaccid lower extremity weakness, back pain, bowel and bladder dysfunction and paraesthesia as a clinical presentations, which are similar to presentations of the index case.

It may be difficult to differentiate spinal intramedullary tuberculoma from other intramedullary lesions such as primary and metastatic spinal tumours and chronic granulomatous diseases like sarcoidosis, brucellosis and histiocytosis. However, the characteristic findings on magnetic resonance imaging (MRI) include low intensity rings with or without central hyper-intensity on T2W images and low to iso-intense rings on T1W images. T2W spinal MRI of our patient showed the typical “target sign” demonstrating low signal center (caseous material) surrounded by high signal rim (peripheral infective granulation tissue) which is a valuable means of differentiating a tuberculoma from other intramedullary lesions1, 11,15,16.

In the management of intramedullary tuberculoma, medical, surgical or combined approaches have been used with good results in different series although there is no consensus on the ideal treatment11, 12,13,16,17. Although some authors recommend only medical treatment, surgery is usually indicated when the diagnosis is uncertain, the lesion is large and is accompanied by rapid deterioration in neurological functions or when there is no response to chemotherapy18. In this case the diagnosis was in doubt pre-operatively which necessitated microsurgical excision which histologically was consistent with granulomatous lesion with central caseation in keeping with tuberculoma. As a general principle in the treatment of CNS tuberculosis, drugs that penetrate the CNS such as isoniazid, rifampin, ethambutol and pyrazinamide should be used16. This combination is usually administered in the intensive phase of 2-3 months followed by a continuation phase for a period of 9-10 months with Rifampicin and INH. There are few controlled studies detailing the specific combination and duration of antituberculous chemotherapy for intramedullary spinal tuberculoma but treatment can be extended for up to 18 months depending on the clinical state and the response of the patient1, 11,19. Our patient made a good recovery as he had normal power in his lower limbs following 8 months of antituberculous medications after surgery.

Conclusions

Intramedullary tuberculoma should be considered in differential diagnosis of intramedullary tumors in this environment. Treatment with anti-tuberculous therapy results in good outcome.

Figure 1. T2 weighted Thoracolumbar MRI of the patient showing circumscribed lesion at D12 and L1 with target sign and spinal cord expansion.

Figure 2. Histological appearance of the lesion showing granulomatous lesion with a central area of caseation.