Teaching Case

A 62-year-old male presented to the neurology outpatient department with progressive complaints of walking difficulty, memory disturbances, restricted eye movements and urinary incontinence of three months duration. There was no history of overt trauma, headache or recent surgical intervention. His vital signs were unremarkable. Clinical examination revealed bradykinesia and upper limb rigidity.

MR imaging was requested for evaluation of Parkinson's disease-like symptoms. MR imaging revealed non-dependent, T1/T2WI hypointense foci in the frontal horn of lateral ventricles (Figure 1a) and temporal horn of right lateral ventricle associated with blooming on T2* GRE images (Figure 1b) suggestive of air foci. No similar air foci were noted in the rest of the visualised intracranial cavity. However, T2 hyperintense contents were appreciated in the left mastoid region and middle ear cavity (Figure 1c).

Subsequently, a corroborative NCCT Head was performed that confirmed hypodense, non-dependent, intraventricular air foci (mean -970 HU) (Figure 2a). Apart from hypodense internal contents noted in the mastoid air cells and middle ear cavity, focal cortical thinning associated with bony erosion/defect was appreciated involving ipsilateral tegmen tympani (Figures 2b and 2c).

Background

Pneumocephalus is defined as pathological intracranial air. Head trauma accounts for more than two-thirds of all cases of pneumocephalus. Spontaneous otogenic pneumocephalus restricted to intraventricular compartment is extremely rare, with less than ten cases reported worldwide [1,2]. It is generally attributed to chronic otitis media, trivial trauma (Valsalva maneuver) or mastoid surgery. The presence of a bony/dural defect and negative intracranial pressure gradient (exacerbated by Valsalva maneuver) have been hypothesised as the primary pathogenetic mechanism causing spontaneous otogenic pneumocephalus with trapped intracranial air simulating “ball-valve mechanism” [3].

Clinical Perspective

While the most commonly reported clinical presentation of pneumocephalus is headache followed by CSF rhinorrhoea, meningeal signs and cranial nerve palsies [4], our patient had none of these symptoms. The imaging was requested for evaluation of Parkinsonism-like symptomatology. Intraventricular pneumocephalus was incidentally detected on imaging.

Imaging Perspective

• MRI – Intracranial air foci are characterised by T1 and T2WI hypointensity that are usually restricted to non-dependent areas of lateral ventricles in the case of purely intraventricular pneumocephalus. These foci show prominent blooming on T2*GRE and SWI images. The presence of T2W hyperintense contents in the mastoid air cells or middle ear cavity should raise the suspicion of an otogenic cause of pneumocephalus, even in the absence of overt otogenic symptomatology.
• CT – CT is of paramount importance in demonstrating the bony defect – most commonly seen along tegmen tympani in reformatted thin sections of the temporal bone.

Management & Outcome

Our unique case presents an unusual radiological profile of pure intraventricular pneumocephalus, a condition exceptionally rare. Remarkably, the patient lacked the typical clinical symptoms associated with this entity.

T2W hyperintense contents in the left mastoid and petrous air cells raised suspicion of otogenic pneumocephalus, prompting a temporal bone HRCT that confirmed tegmen tympani bony defect. The bony defect could be attributed to trivial trauma or chronic inflammation from otitis media and mastoiditis.

It is speculated that factors like Valsalva maneuver, Eustachian tube dysfunction, or frequent nose blowing led to the passage of high-pressure air across this defect from middle ear into the subarachnoid space. In this particular case, conservative treatment with supportive measures was deemed appropriate since the patient remained asymptomatic with no clinical or imaging indications of elevated intracranial pressure, ongoing dural CSF leak or intracranial infection.

Teaching Points

Pneumocephalus on intracranial imaging without overt history of trauma or surgical procedures should be evaluated further to exclude otogenic causes of pneumocephalus, especially in the presence of middle ear/mastoid cell opacification.

Written informed patient consent for publication has been obtained.