Calvarial tuberculosis is rare forming only 1.3 % of the extrapulmonary presentation of TB. It poses a diagnostic challenge especially when located in rare sites like cranial bones. A case of calvarial tuberculosis is being presented for its diagnostic difficulty and rarity.
Tuberculosis (TB) is a very common disease in India. It continues to be among the greatest health problems in developing countries and has an enormous social and economic impact. In India there is 58% reduction in TB mortality rate by 2014 as compared to 1990 level and 55% reduction in TB prevalence rate by 2014 as compared to 1990 level. Tuberculosis incidence per lakh population has reduced from 216 in year 1990 to 167 in 20141.
Tuberculosis may infect any part of the body, but most commonly occurs in the lungs (known as pulmonary tuberculosis). Extra pulmonary TB occurs when tuberculosis develops outside of the lungs. Extra pulmonary TB occurs more commonly in immunosuppressed persons and young children. Common sites are pleura, lymph nodes, abdomen, genitourinary tract, skin, joints and bones, or meninges. Mycobacterium tuberculosis is thought to reach calvarium by haematogenous spread. In this article we describe a case of calvarial tuberculosis in a 78 year old lady.
A 78 year old female presented to outpatient clinic with a forehead swelling of 4 months duration. She was treated for carcinoma of left breast for which she underwent modified radical mastectomy 12 year ago and also received Tamoxifen for 5 years and has been regularly followed up. She also has a history of left sided MCA stroke with right sided weakness for which she is on anticoagulants. She lived with her sister who was receiving treatment for pulmonary Kochs.
On examination it was a soft and fluctuant swelling on her frontal scalp. (Fig 1) Swelling was painless and measured about 6 x 6 cm in dimension with no evidence of pus discharge. No increased ICP features, pupils are equally reacting to light with a GCS of 15/15. A differential diagnosis of metastasis, multiple myeloma, dermoid cyst was made.
FNAC from the swelling was done which yielded a yellowish purulent exudate and was pathologically reported as dermoid cyst. A CT scan of the brain was done to know the extent of the cyst, which revealed bony erosion of the inner/outer table of frontal bone of the skull (Fig 2). The soft tissue mass was overlying the bony lesion with intracranial extension but no intradural extension or mass effect.
She underwent complete excision of the lesion and titanium mesh cranioplasty. The cystic lining was completely excised/enucleated and the bony edges were nibbled and the final defect was reconstructed with titanium mesh. Scalp was closed in layers with a drain insitu and she withstood the procedure well.( Fig 3, 4, 5)
The histopathology was reported as Tuberculosis. Showing epitheloid granulomatous with caesation necrosis and dense infiltration by lymphocytes, plasma cells and macrophages. Langhans giant cells was present. Lamellar bone seen are destroyed by granulomas. Ziehl Neelsen stain for AFB : POSITIVE.
She has fully recovered since then, was started on antituberculosis treatment medications. ( Fig 6 )
Tuberculosis is curable and preventable. It is caused by bacteria mycobacterium tuberculosis that most often affects the lung. All age groups are at risk. People infected with tuberculosis bacteria have a 5-15% lifetime risk of falling ill with TB, however persons with compromised immune system such as people with HIV, malnutrition or diabetes or even people who use tobacco have a much higher risk of getting tuberculosis2. Tuberculosis maybe regarded in 2 categories: active disease or latent disease. About one quarter of the world’s population has latent tuberculosis.
The most common form is pulmonary tuberculosis. Symptoms include mainly cough with sputum, fever, night sweats, loss of weight and appetite. Tuberculosis may also invade other organs called as “extrapulmonary tuberculosis”. Common sites, being lymph nodes, pleura, abdomen, bone and joint, spinal cord and calvarial tuberculosis3. The least common extra pulmonary tuberculosis being calvarial tuberculosis.
Calvarial tuberculosis was first reported by Reid in 18424. Calvarial tuberculosis accounts for 0.2-1.3% of all tubercular osteitis5. It is uncommon even in areas where tuberculosis is endemic. After the advent of anti-tubercular drugs, the incidence of calvarial tuberculosis has been reduced further and with the treatment of the primary lesion, calvarial tuberculosis may not reach the stage of clinical presentation. Thus, calvarial tuberculosis is a rare manifestation of skeletal involvement by tuberculosis. In 1981, Mohanty Et Al reported 156 cases of chronic osteomyelitis of skull in India, of which 22 cases were tuberculosis6.
The younger population is usually at higher risk. 50% were patients younger than 10 years while 75-90% patients were younger than 20 years. Parietal and frontal bones are usually involved due to high cancellous portion, hence explaining why it is rarely seen in infants. Trauma has also been incriminated as a possible cause of skeletal tuberculosis. This could possibly be due to rich vascular supply of skull bones or unmasking of latent infection by trauma or low resistance7. Early signs are usually absent in the disease. The appearance of a painless fluctuant swelling is the most common presentation and usually the first symptom. A soft swelling of the scalp with erosion of the underlying bone is very characteristic. Any clinical findings suggestive of intracranial extension like seizures, venous sinus thrombosis, and meningitis are rarely observed.
Montoux test and raised ESR are good markers and may give a diagnostic clue to TB. However Montoux test maybe negative in 10%patients while ESR maybe normal in similar number of patients7. CT and MRI are recommended to asses extent of bone involvement, scalp swelling and degree of intracranial extension. Radiological findings which are very valuable tools to reach a diagnosis are thought to be only suggestive and not diagnostic. Demonstration of AFB (acid fast bacilli) in the smears or biopsy specimen is diagnostic. But in severe necrosis in some specimens AFB may not be demonstrated in many cases.
Management includes predominantly ATT (anti tubercular treatment) and surgery. Surgical management by debridement and curettage alone showed good results before the advent of ATT. surgery is indicated for diagnosis, for removal of sequestration or epidural collections, for patients with discharging sinuses or large collections of caseating material leading to mass effect or increased intracranial pressure. Recent studies advocate that combination therapy (ATT and surgery) is better as extensive areas of diseased bone may be source of tubercle bacilli unless surgically excised. Prognosis depends upon gravity of the associated tuberculosis lesion and local extent of the disease.
To conclude, calvarial tuberculosis is a rare presentation of a common disease. Scalp swelling is the most common presentation. CT and MRI are main radiological investigation. Including certain laboratory investigation especially when there is high index of suspicion. However definitive diagnosis depends on AFB, culture and biopsy report. Surgical debridement and ATT is the mainstay management for this unusual presentation.