CASE REPORT

A 50 year-old woman, treated 20 years ago for pulmonary tuberculosis, was admitted to our institution in March , 1996 with a scalp swelling over the left frontal area and left sided headache developing during a 3 months period. On physical examination there was a fluctuant, non tender mass in the left frontal region measuring 4 x 5 cm. There was a sinus discharging purulent material from the swelling. She was afebrile and there were no palpable lymph nodes in the head and neck region. General and neurological examination revealed no abnormalities. Plain radiographs of the skull showed a localized area of bony defect of 2 x 3 cm underlying the scalp swelling (Fig 1). Bony defect and adjacent enhanced epidural collection were detected on computed tomography scan of the skull (Fig. 2).

Other abnormal biological parameters were an increasing erythrocyte sedimentation rate (60 mm at the first hour) and positive tuberculin skin test (12 mm). At craniectomy, we have found purulent material in the subgaleal space, bony sequestrum and epidural collection with granulation tissue. The craniectomy was enlarged until the healthy bone was seen, the epidural collection removed.

Exploration of the intradural space was not undertaken nor was cranioplasty. No acid fast Bacilii were seen. A colony of staphylococcus aureus grew in the bacterial cultures. Histological examination of the bone and epidural collection revealed chronic inflammatory cells consisting of multiple confluent epitheloid granulomas with central caseation, typical of tuberculous granuloma (Fig. 3).

Postoperative antituberculous chemotherapy with rifampicin (10 mg / kg/ day),isoniazid. (5.mg/kg/day) and pyrazimanide (32mg/ kg/ day) was commenced in association with flucloxacillin 6g every day for three weeks. Pyrazinamide was withdrawn after two months of therapy while the remaining antituberculous medications were continued for 9 months . There was no recurrence of infection after 18 months follow up.

	Figure 1 — Lateral skull X-ray showing bone erosion		Figure 2 —CT scan showing bony erosion and soft tissue collection under the scalp

	Figure 3 — Photomicrograph of the specimen showing caseation necrosis

DISCUSSION

Tuberculosis is a chronic, bacterial infection caused by Mycobacterium tuberculosis characterized by the formation of granulomas and cell mediated hypersensitivity. There are approximately 30 million active cases in the world, 10 million new cases occur annually. It causes 6% of all deaths world-wide. It remains a significant health problem in developing countries.5,8,13 Because of the migration of a large number of people from endemic areas and increasing incidence of acquired immunodeficiency syndrome, there is an increase in the incidence of TB in western countries. The skull is not a frequent site of TB. (2,8,9,13) It is estimated to be from 0.2% to 1,37% of tuberculosis affecting the bone. (12) Since the Strauss's review in 1933(11), some short series and numerous case reports have appeared. (2,3,4,8,9,13) It is essentially a disease of the young, 75% of patients are under 20 years of age (11). It is commonly associated with tuberculosis elsewhere in the body. (2,3,8,9,11,13) Tuberculosis of the skull is always secondary to a hematogenous spread from a primary active or latent focus which typically is located in the lungs. This patient had pulmonary tuberculosis 20 years ago. Frontal and parietal bones are the most involved areas. The lesion spreads through the diploe with destruction of the inner table and formation of epidural granulation tissue. (5) The dura is extremely resistant to cranial tuberculosis (11) but few cases are associated with intradural tuberculosis such as meningits or brain tuberculomas. (6,11) The usual clinical manifestation is swelling of the scalp which is of insiduous onset. The swelling may become fluctuant and may burst, producing a non healing sinus. Pain may or may not be present (7,13) X-Ray of the skull characteristically shows osteolysis and osteoporosis. If there is secondary infection or if the disease is in the healing stage, osteosclerosis may also be seen. CT scan shows, extra and intra cranial enhancement of soft tissue mass in addition to bone destruction. Dura matter is never penetrated by the granulation tissue. (11)

Positive history of pulmonary tuberculosis, increase of erythrocyte sedimentation rate and positive tuberculin test inspite of the growth of staphylococus aureus confirmed subsequently by histopathological study.

Treatment involves surgery and antituberculous therapy. It is necessary to excise all diseased bones. However total excision of granulation tissue is not necessary Thee indications of surgery appear to be extradural collection, presence of a large sequestrum and discharging sinus as in our case. Surgery would also be indicated if there is doubt about the diagnosis. 8,13 We believe that cranioplasty is not an appropriate approach immediately but it could be done after healing and normalization of erythrocyte sedimentation rate. In children cranioplasty is not recommended because ossification of bony defects could supervence spontaneously.

REFERENCES

1.	Farrel VJ, Brain Stem tuberculoma in adult patients: Diagnosis and treatment Surg Neurol 1990, 34:383-9.
2.	Gamboa F, Gomez Mateos J, Lopez-Cortes LF, Lozano de leon F, Carcia BragadoF, tuberculosis of the skull: an unusual manifestation; Tubercle and Leng disease, 1994, 75(2):156-157
3.	IPM. Tusi E. Wong KL, Jones B, Pung CF, Ngan H, disseminated skeletal tuberculosis with skull involvement; Tubercle and Lug Disease: 1993, 74 (3) 211-4
4.	Jamjoom ZB Assaf HM, Hamid F, Haddad Qet al intracranial epidural tuberculoma presenting as a scalp swelling, Burg neurol 1993; 42:322-5.
5.	Leroux PD, Griffin GE, Marsh HT, Winn HR tuberculosis of the skull - a rare condition case report and review of literature Neurosurgery 1990, 26:851-6.
6.	Meng CM, Wu YK: tuberculosis of the flat bones of the vault of the skull. J Bone joint Burg (Br)1942, 24:41-453
7.	Miles J, Hughes B: tuberculous osteilis of the skull Br Surg 1970, 57:673-9
8.	Nicholson RA, twenty years of bone and joint tuberculosis in Brad ford . A comparison of the disease in the indigenous and Asian population, J. Bone Joint Surg. 1974, 56B: 760-765
9.	Pelteret RM, tuberculous osteitis of the skull Annals of Tropical Pediatrics: 1989, 9(1)40-2
10.	Prinsloo JG, Kristen GF: tuberculosis of the skull vault. S Afr Med J, 1977; 5 248-250
11.	Strauss DC Tuberculosis of the flat bones of the skull - Surg Gynaecol obstet 1933, 57: 348-398.
12.	Tirona JP, The roentgenological and pathological aspects of tuberculosis of the skull 1954 72: 762-768
13.	Tyagi AK, Kirollos RW, Kang NV, Tuberculous osteilis of the skull: a case report and review of the literature , British journal of neurosurgy 1996; 10(4): 339-401