On examination, she looked very ill with a tense warm and tender swelling on her forehead and the anterior half of her scalp. She had bilateral periorbital oedema and opened her eyes with great difficulty. She was conscious and well oriented but not interested in her surroundings with occasional inappropriate smiles. She had slight left facial (upper motor neuron) palsy and a weak left lateral rectus muscle. Her neck was stiff and Kernig's sign was positive. Respiratory and cardiovascular systems were normal.

There were no abnormal abdominal findings. Fundoscopy showed a normal optic disc but dilated veins. Plain x-ray of the skull showed lytic lesions in the frontal bones. Findings of CT scan of the head are shown in Figure 1.

She was managed with IV ceftriaxone, flucloxacillin, and metronidazole. The neurosurgeons were invited for surgical intervention. In theatre seven hundred milliliters of pus was drained from the subgaleal abscess and one hundred milliliters from the frontal abscess. Sequestrectomy of the mid-frontal bone was done. Cultures done on the pus isolated no organisms.

The bone separating the frontal sinus from the anterior cranial fossa and the orbit are often quite thin and the interrelated venous drainage system of these areas form the anatomic basis of serious orbital and intracranial complications¹. Most cases of skull osteomyelitis are related to trauma and spread from adjacent sites especially the frontal sinus. There are occasional reports of haematogenous origin of infection². Epidural empyemas are usually associated with osteomyelitis of the skull. Epidural extension of skull infection separates the dura mater from the inner table of the skull thus interfering with the major blood supply to the inner table of the skull and predisposing the bones to widespread infection. The dura is initially resistant to infection but later yields with resultant meningitis and abscess. The Central Nervous System (CNS) is vulnerable to destruction by infectious processes and is incapable of mounting a significant immune defense itself¹. A gliotic zone develops around the site of infection but does little to limit spread of infection³.

In acute osteomyelitis, the patient is toxic with tender swelling over the bone involved, called Pott's puffy tumour. Chronic osteomyelitis often presents as a lump on the head. Brain abscess may mimic any other intracranial space-occupying lesion with its features of seizures, focal deficits and other features of raised intracranial pressure such as headaches, and vomiting. The patient may present with a low-grade fever, leucocytosis, and raised ESR and C-reactive protein. CT scan shows contrast-enhancing rim with a non-enhancing hypodense center. CSF examination is contraindicated in patients with suspected suppurative intracranial space occupying lesion and the results are non-specific.

The majority of brain abscesses occur in the first two decades of life because of the predisposition of this age group to sinus and middle ear infections. Sinusitis has surpassed middle ear and mastoid disease as the most common source of infection in patients with brain abscesses. The frontal sinus is the most common followed by ethmoid, sphenoid and maxillary sinuses.

Despite advances in neuroradiological imaging techniques and antimicrobial chemotherapy⁴ the incidence of cerebral abscesses may be increasing with a growing number of opportunistic infections in immunocompromised patients^{4, 5}.

The diagnosing of intracranial complications of sinusitis requires a high index of suspicion, imaging of brain and paranasal sinuses and aggressive intervention⁶.