Intra-medullary tubercular abscess with spinal dysraphism: An unusual case.

Spinal intramedullary tubercular abscess itself is a rare entity. Very few cases have been reported. We report a case of a 4-month-old female with a dermal sinus in lower back since birth, intermittent fever for 2 months, acute onset paraparesis and bowel bladder involvement showing an intramedullary contrast enhancing lesion extending from D11 to S2 level with low lying conus, and a subcutaneous tract in lower back at S2 level extending from skin up to the sacral canal on magnetic resonance imaging of the spine. Drainage of abscess and biopsy revealed tubercular infection on histopathology. The patient made a good recovery with anti-tubercular treatment and physiotherapy. The source of tubercular infection could not be established. The baby had received Bacillus Calmette-Guérin vaccination at birth and the possibility of vaccination associated tubercular infection could not be ruled out.

Introduction

Intramedullary spinal cord tubercular abscess are very rare. The first description in 1830 by Hart,[1] only about 100 cases of intramedullary abscess have been reported. This condition is very rare in children, and it is important to remember this entity, if detected and treated early, has a favorable prognosis.

Case Report

A 4-month-old female baby presented to us with history of intermittent fever since 2 months; lethargy, weak cry, refusal of feeds since 1-week; acute onset weakness of both lower limbs since 3 days. The fever was intermittent for which she had been hospitalized twice with no relief of fever even after having received several antibiotics. The mother had also noticed that the baby cried excessively during micturition. According to the mother, at birth there was a small midline swelling over the sacral region with discoloration of overlying skin and a sinus with tuft of hair, but no discharge. Ultrasonography of the spine at 2 days of birth showed spina bifida at L4 level. On examination, she was afebrile, pale, and irritable, with flaccid paraplegia and a midline sacral dimple with dermal sinus. The anus was patulous with perianal redness. There were no signs of meningeal irritation. The chest X-ray and blood investigations were normal.

The magnetic resonance (MR) scan of the brain was normal while that of the spine showed an intramedullary high signal on T2-weighted images with poorly defined marginal enhancement on T1-weighted images extending from D11 to S3 level and a low lying conus with tethered filum terminale. On sagittal sections, a subcutaneous tract in lower back at S2 level extending from the skin up to sacral canal was noted. Also noted was an over distended bladder [Figure 1].

Figure 1

T2 sagittal section with contrast showing well defined abscess cavity with a full bladder

An L2–L4 laminectomy was done. The L5–S1 laminae were fibrous. On opening the dura, an enlarged and congested conus was noted. A midline myelotomy opened a large intramedullary cavity containing pus lined with granulation tissue. The abscess was drained; biopsy of the granulation tissue was taken and sent for examination. It was found that the dermal sinus was communicating with lower end of the dural tube, which was excised and sent for examination. The thickened tethered filum terminale was also sectioned.

The pus stained positive for acid-fast bacilli (Ziehl Neelsen stain) while the Gram stain was negative [Figure 2]. On histopathology, the wall of the abscess composed of necrotizing granulomatous inflammation, suggestive of tuberculous infection; while the dermal sinus examination revealed chronic inflammation and fibrosis. The pus culture was negative. Mycobacterium tuberculosis (MTB) was detected on MTB DNA polymerase chain reaction. The baby responded well to anti-tubercular treatment. A retrospective search for finding out the source of infection proved unsuccessful. The patient was a 4-month-old baby having received Bacillus Calmette–Guérin (BCG) vaccination at birth, with no other focus of tubercular infection elsewhere in the body. The mother with all family members, including the servants were screened for tuberculosis with chest X-ray and three serial early morning sputum examinations, but none tested positive. She was discharged on anti-tubercular treatment and physiotherapy. Follow-up MR scan showed good resolution of the intramedullary abscess.

Figure 2

Ziehl Neelsen stain showing acid-fast bacilli

Discussion

Intramedullary spinal cord abscesses are rare in both adults and children. Simon et al. in a review of intramedullary spinal cord abscess in children found slight male predominance (55%) with median age of 36 months (range: 18 days to 7 years), while our patient was a 4-month-old female infant.[2]

Staphylococcus and Streptococcus were the most commonly isolated organisms in 100 cases of intramedullary pyogenic abscesses reported by Desai et al.[3] Intramedullary spinal tubercular abscess is quite rare. Only four cases demonstrated MTB of the total 77 cases of intramedullary abscesses reported.[45] Intramedullary spinal cord tuberculoma due to MTB infection tends to occur predominantly in young people of developing countries and are associated with systemic diseases, usually pulmonary.[6] Intramedullary tuberculosis is always secondary to pulmonary tuberculosis. However, some cases may present with isolated extrapulmonary forms.[67] In our case, we could not find a focus of tuberculous infection elsewhere. Furthermore, there were no skin lesions over the back, which ruled out the possibility of cutaneous tubercular infection. In children, hematogenous spread from a variety of sources does occur, but preexisting congenital defects in spinal cord development are a more common means by which infection occurs.[6] The dermal sinus has been increasingly observed as a source of intramedullary spinal abscess in the antibiotic era, likely because other deep seated and adjacent infections are more effectively eliminated before they spread to the spinal cord. Staphylococcus aureus was reported to be the commonest offending organism in the case of abscess associated with dermal sinus in a recent series.[6] In our patient, Gram stain and culture examinations did not reveal the common abscess forming organisms. Our patient had a dermal sinus in-communication with the dural tube and an intramedullary abscess, which was found to be tubercular, though no hypothesis or explanation of the pathophysiology could be stated.

Prognosis is poor if treatment is delayed. Prompt surgical drainage of abscess with appropriate antibiotics and anti-tubercular treatment is recommended.[6] Our patient made a good recovery after drainage of the abscess and anti-tubercular treatment. The patient had only received BCG vaccination at birth, and while the source of this tubercular abscess formation could not be identified, the possibility of vaccination associated tubercular infection could not be ruled out.

At 3 years, she has a left foot deformity with limping gait and a neurogenic bladder. She has undergone orthopedic corrective surgery for the left foot deformity and requires clean intermittent catheterization as management of her neurogenic bladder.