Fact-sheet: Pneumoencephaly
Updated on 09/17/2021 at 12:16 PM
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Definition
Presence of air within the cranial vault. Variable morphology, forming small to large collections. > Pneumatocele if focal. Possible location in any compartment: -extra-axial: Epidural, Subdural, Subarachnoid. -intra-axial: Cerebral parenchyma, ventricular system. -intravascular. Etiology: -post-traumatic: the most common – 75%. Fracture of the calvarium or facial sinuses. Penetrating trauma. -Neoplasm with sinus invasion: 13%. Osteoma (frontal predilection), pituitary adenoma, mucocele (frontal predilection), adenocarcinomas. -Infection: 9%, sinusitis, apical petrositis. Gas-producing bacteria. -Surgery/iatrogenic: 4%. Notably, 100% of patients who have undergone supratentorial surgery present with pneumoencephaly within the first 48 hours. A form to distinguish: Tension or compressive pneumoencephaly -"Mt Fuji sign": Subdural pneumoencephaly compressing the frontal lobes bilaterally, producing the silhouette of Mount Fuji. -"Air bubble sign": multiple small pneumoencephaly bubbles distributed throughout the ventriculocisternal system.
Clinical features
-Asymptomatic.
-Headaches reported.
-Most often those of the incident trauma.
-Tension pneumocephalus: possible impaired consciousness and focal deficits.
CT
-Collection(s) of very low density (-1000 HU).
-Distribution: intra-axial, extra-axial, intravascular, confluent or not.
-Search for etiology: Fracture, infection, sinus tumor, iatrogenic-surgical cause.
-Search for signs of compression.
MRI
>Seen as absence of signal on all sequences.
>Induced artifacts.
-FLAIR: evaluation of sinusitis, apical petrositis.
-T1 with gadolinium: expansile process of the facial sinuses.
Management
Pneumoencephaly is usually not a problem in itself > find the cause.
-Spontaneous complete resorption or resorption after treatment of the underlying cause.
-Compressive pneumoencephaly: possible decompressive surgery, closure of osteomeningeal defects.
>Caution: Air transport of patients is problematic. Indeed, the decrease in cabin pressure leads to an approximately 30% increase in the volume of the pneumoencephaly (e.g., at 8000 ft), all within a non-distensible cranial vault