CNS complications of frontal sinusitis

Introduction:

The advent of effective antibiotics has reduced the incidence of intracranial complications following sinus infections. Still these complications do occur carrying with it significant morbidity and mortality. Studies have shown that frontal sinusitis is still the commonest cause for intracranial complications followed by ethmoid,sphenoid and maxillary sinus infections.

Route of spread:

Infections of frontal sinus commonly spreads to the brain by haematogenous route. This spread of infection is further facilitated by the presence of small valveless diploic veins (Veins of Breschet). These veins extend through the posterior table of the frontal sinus directly contributing to the formation of venous plexus around dura and periosteum. Bacterial emboli can traverse through these venous plexus seeding the remote intracranial sites causing meningitis, epidural / intracerebral abscess/ subdural empyema. Sometimes thrombophlebitis can develop causing superior sagittal sinus thrombosis and cavernous sinus thrombosis. Cavernous sinus thrombosis is a life threatening situation and must be identified and treated on an urgent basis.

Frontal sinusitis commonly involves people of adolescent age group coinciding with the rapid development and pneumatization of frontal sinus cavity. It has been shown that 3-4% of patients with acute frontal sinusitis may land up with intracranial complication.

Signs & symptoms:

1. Acute / progressive headache

2. Presence of fever

3. Presence of focal neurological deficits

4. Change in mental status

5. Lethargy

6. Seizure

7. Coma

The clinical presentation may actually vary with the site of involvement. In the case of frontal lobe involvement the only manifestation could be the presence of subtle change in the personality of the patient. It should also be pointed out that the patients with intracranial complications following sinus infections may not complain of symptoms pertaining to the nose / sinuses. They may give history of symptoms pertaining to frontal sinus infection like head ache in the frontal region and tenderness over the frontal sinus region.

Superior sagittal sinus thrombosis: This condition is frequently associated with nausea and vomiting. There may be presence of severe head ache.

Pott’s puffy tumor:

This condition is known to occur very rarely. This is caused by osteomyelitis of anterior table of frontal bone causing oedema of forehead or even a pericranial abscess.

Imaging:

All patients suspected of intracranial complication following frontal sinus infection should undergo CT scan of nose and paranasal sinuses. Contrast CT will accurately pick up intracranial complications.

Role of Lumbar puncture: This procedure should be weighed against the risk of herniation of brain. It should be performed only after ruling out elevated intracranial pressure.

Note:

In patients with sinusitis the presence of following sign indicates meningitis unless other wise proved.

Persistent high fever Severe headache Meningismus Photophobia Irritability Altered mental status

It should also be remembered that meningitis is very rarely caused by isolated frontal sinusitis. If present it could indicate the presence of ethmoid / sphenoid sinusitis, intracranial abscesses occurring in the epidural space / subdural space / intraparenchymally.

Epidural abscess:

Commonly occurs behind the posterior table. It should be borne in mind that the dura is loosely attached in this area allowing pus to collect and expand. Symptoms are usually mild till the collection becomes large enough to cause an increase in the intracranial pressure. These patients may manifest with forehead oedema and tenderness. The proximity of orbit may cause orbital swelling to occur. Other than elevated intracranial pressures the lumbar puncture will reveal normal results.

Subdural abscess:Subdural space is a potential space between the dura and arachnoid. This condition may be associated with increased intracranial pressures, elevated protein / pleocytosis / normal glucose / lack of organisms in CSF studies. The arachnoid prevents extension of infection to leptomeninges. Pus in this space precipitates vasculitis andseptic thrombophlebitis. The inflammatory oedema and venous obstruction causes increased oedema and venous obstruction causing a further increase in the intracranial pressures.

Subdural abscess usually present with:

Increasing headache Fever Elevated WBC count Meningeal signs

Late stages of subdural abscess may lead to cortical signs and symptoms like:

Hemiparesis Hemiplegia Cranial neuropathies Seizure

Increased intracranial tension causes:

Nausea Vomiting Bradycardia Hypertension Decreased levels of consciousness

Death may eventually occur due to transtentorial herniation following lumbar puncture procedure.

Cavernous sinu sthrombosis:

Findings include

Proptosis Chemosis Ophthalmoplegia Cranial nerves II & III palsy Progressive visual loss Contralateral involvement ispathognomonic.

Brain abscesses:

Due to frontal sinusitis commonly arise from septic emboli that travel to the frontal lobe via retrograde venous communications. Since white matter has poor blood supply in comparison to grey matter, abscesses usually occur here and becomes encapsulated over weeks. Brain abscesses may be silent till it ruptures into the ventricular system causing rapid death.

Management:

1. Admission to hospital

2. CT scan both plain and contrast

3. Intravenous broad spectrum antibiotics

4. Drugs that reduce intracranial tension (Mannitol)

5. Frontal sinusotomy if general condition permits