What is the appropriate management for a patient with air in the interhemispheric fissure, potentially due to head trauma, recent neurosurgical procedures, or underlying medical conditions?

Management of Interhemispheric Fissure Air

For patients with air in the interhemispheric fissure following head trauma, conservative management with close observation is appropriate for most cases, reserving urgent surgical decompression only for those with clinical signs of tension pneumocephalus or deteriorating neurological status.

Initial Assessment and Diagnosis

• Pneumocephalus occurs in 0.5-1.0% of head trauma cases and is diagnosed radiographically by CT scan, which can reveal even very small quantities of intracranial air 1
• The presence of air in the interhemispheric fissure specifically indicates subarachnoid or subdural air accumulation, often associated with craniodural fistula 1
• Most patients present with nonspecific symptoms such as headache, requiring a high index of suspicion in recent head trauma 1
• The pathognomonic "succussion splash" (audible sloshing sound with head movement) is diagnostic when present, though uncommon 1, 2

Clinical Differentiation: Simple vs. Tension Pneumocephalus

Simple pneumocephalus:

• Patients remain alert and ambulatory without clinical signs of raised intracranial pressure 3
• No evidence of mass effect or neurological deterioration 3

Tension pneumocephalus (Mount Fuji sign):

• Radiological findings show compression of frontal lobes and widening of the interhemispheric space 3
• Ball-valve mechanism allows air entry but prevents exit, creating mass effect 1, 2
• May present with altered consciousness, though not always clinically apparent 3

Management Algorithm

Conservative Management (First-Line for Most Cases)

• Noninvasive therapy is appropriate for simple pneumocephalus, allowing the craniodural defect to heal spontaneously 1
• Maintain patient in semi-upright position to facilitate air resorption
• Avoid maneuvers that increase intracranial pressure (Valsalva, sneezing, coughing) as these can worsen pneumocephalus 4
• Serial neurological examinations to monitor for deterioration 3
• Follow-up CT imaging if clinical status changes or symptoms persist 4
• Most cases resolve within 10-16 days with conservative management 3, 4

Surgical Intervention (Reserved for Specific Situations)

Immediate operative repair is required when:

• Clinical signs of raised intracranial pressure develop 3
• Progressive neurological deterioration occurs 1
• Persistent CSF rhinorrhea or otorrhea indicates ongoing craniodural fistula 5
• Tension pneumocephalus with mass effect despite conservative measures 3

Critical Airway Considerations

• If airway management is required, use oral route exclusively - nasopharyngeal airways and nasotracheal intubation are contraindicated due to risk of inadvertent intracranial placement through basilar skull fractures 6
• Avoid high-flow nasal oxygen in patients with basilar skull fractures, as this can induce or worsen pneumocephalus 6
• Maintain systolic blood pressure >110 mmHg and MAP >80 mmHg if concurrent traumatic brain injury is present 7
• Target PaCO₂ between 4.5-5.0 kPa (35-40 mmHg) to maintain normoventilation unless signs of cerebral herniation develop 7, 8

Monitoring and Follow-Up

• Re-evaluate CT imaging if new symptoms develop, particularly after events that increase intracranial pressure (sneezing, straining) 4
• Monitor for delayed pneumocephalus development, which can occur days after initial trauma 4
• Assess for associated injuries including subarachnoid hemorrhage, epidural/subdural hematomas, and skull base fractures 5
• Document presence of single versus multiple air bubbles and anatomical location (epidural, subdural, subarachnoid, or intracerebral) 5

Common Pitfalls to Avoid

• Do not assume all pneumocephalus requires surgical intervention - the majority of cases without tension physiology resolve spontaneously 1, 3
• Avoid nasogastric tube placement in patients with suspected basilar skull fractures and pneumocephalus 6
• Do not discharge patients with pneumocephalus without clear follow-up instructions to avoid Valsalva maneuvers 4
• Recognize that radiological tension pneumocephalus (Mount Fuji sign) does not always correlate with clinical tension physiology - base surgical decisions on clinical status 3