Non-surgical resolution of pneumocephalus following a sneeze

Summary

Pneumocephalus is defined as the abnormal presence of air in the intracranial cavity. Pneumocephalus is most commonly caused by trauma, but there are rare reports of pneumocephalus secondary to allergy-induced sinusitis. In this report, we present a woman in her 60s who presented to the emergency department with a chief complaint of headache after experiencing a ‘popping’ sensation in her ears while sneezing. Over the course of a day, she began experiencing severe pain across the forehead along with copious amounts of clear rhinorrhea. A head CT without contrast was ordered, and findings revealed large amounts of intracranial air visualised diffusely throughout the subarachnoid spaces and the anterior horn of the left lateral ventricle. A diagnosis of pneumocephalus was confirmed. This patient made a full recovery without surgical intervention. Standard conservative therapy included bed rest, head elevation, avoidance of activities that increase intracranial pressure and antibiotic prophylaxis for meningitis.

Background

Pneumocephalus refers to the presence of air in the intracranial cavity via a dural tear that allows abnormal air introduction. In a review of 295 patients with pneumocephalus, trauma was the most common cause (75%).¹ Rarer possible mechanisms include the Ball-valve mechanism from straining, coughing, sneezing and Valsalva or cerebrospinal fluid (CSF) leakage creating negative pressure with resulting air entry.² There are few published reports of allergy-induced sinusitis leading to spontaneous pneumocephalus with pneumoventricle and no osseous destruction. Here, we present a case of significant pneumocephalus presumably due to sinonasal-intracranial communication and concomitant CSF rhinorrhea that was resolved with conservative management.

Case presentation

A woman in her 60s presented to the emergency department with a chief complaint of headache. She had a medical history of hypertension, chronic obstructive pulmonary disorder and type 2 diabetes mellitus. She was sneezing violently when she felt a ‘popping’ sensation in the right ear, pain behind the eyes bilaterally and pain across the forehead. She described the sensation as a dull tightness with mild severity. At that time, she experienced copious amounts of clear rhinorrhea. The next morning, she woke up from sleep with intensified pain across the forehead that was not relieved by a one-time dose of aspirin 520 mg. The pain progressively worsened over the day, and she developed photophobia, phonophobia, nausea and vomiting. She denied numbness, weakness, changes in vision, changes in hearing sensation, dyspnoea, incontinence or loss of consciousness. The patient’s physical exam was unremarkable. Laboratory evaluation included a complete blood count, which revealed a low platelet count of 80 * 10ˆ9/L. A head CT without contrast was ordered to rule out haemorrhagic stroke. Findings revealed large amounts of intracranial air diffusely throughout the subarachnoid spaces and anterior horn of the left lateral ventricle (figures1 2). After these results, neurosurgery was consulted to explore surgical interventions. MRI of the brain and face CT were ordered to evaluate the skull base for abnormalities and the sinuses for infection or neoplasm. A brain MRI with contrast revealed extensive pneumocephalus with a mild mass effect on the frontal pole with no other abnormalities observed (figure 3). A face CT without contrast in the bone window revealed no osseous destruction, intact sinuses, normal nasal septum and patent ostiomeatal complexes (figure 4). On the second day of admission, otolaryngology was consulted and a nasal endoscopy using a flexible laryngoscope was performed for further evaluation of the sinus passages. Findings revealed normal bilateral anatomy, and clear rhinorrhea was determined to be spontaneous CSF leakage with the presence of B2-transferrin. Neurosurgery and otolaryngology decided against surgical intervention due to the lack of acute pathology causing pneumocephalus and CSF rhinorrhea.

Figure 1. Head CT without contrast: air in subarachnoid spaces and left anterior horn.

Figure 2. Sagittal head CT: diffuse air pockets.

Figure 3. Brain MRI with contrast: pneumocephalus compressing the right frontal lobe.

Figure 4. Face CT: imaging revealed no bone abnormalities or fractures.

Differential diagnosis

• Sinusitis: inflammation or infection of the paranasal sinuses, often causing sinus pain, nasal congestion and discharge. While sinusitis can cause headaches and facial pain, it is typically associated with nasal symptoms like congestion and purulent discharge.

• Intracranial haematoma: a collection of blood between layers of the brain and skull, usually caused by trauma or increased arterial pressure. Haematomas cause similar symptoms due to blood, not air, and appear different on imaging.

• Hydrocephalus: an abnormal accumulation of CSF within the ventricles of the brain, leading to increased intracranial pressure. Hydrocephalus is characterised by enlarged ventricles on imaging due to fluid accumulation, not air. Symptoms of hydrocephalus often include headache, nausea, vomiting and gait disturbances, which differ from the presentation of pneumocephalus.

• Intracranial tumour: a mass or growth of abnormal cells in the brain, which can cause symptoms depending on its size and location, such as headache, seizures or focal neurological deficits. Brain tumours are typically seen as solid or cystic masses on imaging, not as air pockets. They may cause a mass effect or shift midline structures, which is different from the air-related compression seen in pneumocephalus.³

Treatment

The patient was treated with conservative therapy which included bed rest, head elevation and avoidance of activities that increase intracranial pressure (eg, sneezing and straining). The patient was prescribed 2 weeks of amoxicillin-clavulanate 875 mg two times per day for meningitis prophylaxis along with supportive treatment of antiemetics and analgesics as needed.

Outcome and follow-up

A repeat head CT performed 2 days after the patient’s initial presentation revealed complete resolution of pneumocephalus and no residual air in the intracranial space (figure 5). The patient was educated to avoid straining, coughing with the mouth open, heavy lifting or strenuous activity and was discharged 3 days after admission to the hospital. The patient was seen for a follow-up appointment with neurosurgery 1 month after discharge and experienced complete resolution of CSF rhinorrhea or other symptoms at that time. The patient did not experience permanent neurological deficits. Additionally, an outpatient referral to an ear, nose and throat skull base surgeon was made in order to evaluate if a skull repair would be needed.

Figure 5. Repeat head CT showing resolution of pneumocephalus.

Discussion

Although the presentation of pneumocephalus is ill-defined, presenting symptoms can include headache, CSF rhinorrhea and papilledema.⁴ These symptoms are consistent with the presentation in our patient. Spontaneous pneumocephalus without associated trauma is rare. The reported incidence accounts for 0.6% of all causes of pneumocephalus, and only 30 cases are reported in the literature to date.⁵ Most of these cases are caused by increased intra-abdominal pressure (Valsalva and sneezing) or environmental changes in pressure (scuba diving and aeroplane flights). In the case of our patient, spontaneous pneumocephalus was most likely caused by increased intra-abdominal pressure due to repeated sneezing. Pneumosinus dilatans describes an air-filled paranasal sinus without evidence of osseous destruction. It most commonly affects the frontal sinus with a one-way valve allowing air to enter the sinus but not exit, leading to air trapping and expansion. Lee et al reported rare cases of patients complaining of a ‘popping feeling’ in the occipital area after repeated episodes of sneezing that forced air into the intracranial cavity leading to spontaneous pneumocephalus, consistent with our patient’s presentation.⁶

Head CT is the gold standard for initial imaging of acute central nervous system symptoms (vomiting and severe headache). If the pneumocephalus causes increased intracranial pressure, it is subsequently diagnosed as a tension, rather than simple pneumocephalus.⁷ There are two classic signs of tension pneumocephalus on non-contrast head CT: the Mount Fuji and air bubble signs. The Mount Fuji sign represents the accumulation of air in the frontal space with consequent separation of the two frontal lobes. The air bubble sign refers to the presence of numerous air bubbles in cisterns due to a tear in the arachnoid membrane because of increased tension in the subdural space.⁸ Our patient’s head CT revealed findings consistent with the air bubble sign demonstrating obvious extradural air creating a mass effect of the right frontal lobe.

Two theories have been postulated to describe the pathophysiology behind the formation of pneumocephalus. The ball-valve mechanism refers to a dural tear created by repeated sneezing or nose blowing that acts as a uni-directional valve, with resulting increase in intracranial pressure. The ‘inverted bottle’ mechanism refers to a defect in the skull base or meninges allowing CSF leakage which reduces the intracranial pressure relative to atmospheric pressure and draws air into the intracranial space. Skull base trauma, history of neurological or sinus surgery, and erosion from infection are common causes. Our patient represents a rare presentation of pneumosinus dilatans leading to the ball-valve mechanism of high air pressure from sneezing driving air into the intracranial cavity with concurrent CSF leakage leading to the inverted bottle mechanism.⁶

Initial management of a patient with pneumocephalus is usually conservative as the air will escape on its own. Conservative treatment includes bed rest, placing the patient at 30 degrees, avoiding Valsalva manoeuvres, analgesics, osmotic diuretics and high-flow oxygen if needed. If a tension pneumocephalus develops with compression of the vital respiratory centres, decompression is urgently required. Needle aspiration via burr hole or craniotomy may achieve pressure relief.³ On serial imaging, our patient’s pneumocephalus resolved within 2 days and conservative therapy of bed rest, head elevation and avoidance of increased intracranial pressure (straining, coughing with open mouth, heavy lifting strenuous activity) was recommended.

Learning points.

• Nontraumatic spontaneous development of pneumocephalus is a rare but potentially life-threatening condition.

• Valsalva manoeuvres such as sneezing or coughing, that increase intracranial pressure, have been reported as causes of pneumocephalus.

• Standard conservative therapy for pneumocephalus includes bed rest, head elevation and avoidance of activities that increase intracranial pressure.