Head & neck imagingCase Type
Maha Ibrahim Metwally1, Mohammad Abd Alkhalik Basha2, Alsayed Abdulmageed3Patient
12 years, male
A 12-year-old male patient attended the otorhinolaryngology outpatient clinic complaining of continuous left ear discharge. The patient reported a past history of recurrent attacks of bacterial meningitis. Clinical examination revealed normal auricle and no clinical facial nerve palsy. There was no past history of trauma, surgery or chronic medical problems.
Computed tomography (CT) images in axial and coronal planes show abnormal bulbous enlargement of the left geniculate ganglion with a dilated labyrinthine segment of the facial nerve canal and osseous dehiscence of the bone that separates the geniculate ganglion from the middle ear cavity (Fig. 1 and 2).
Magnetic resonance imaging (MRI) examination using heavily T2-weighted in axial, coronal and sagittal oblique planes and contrast enhanced T1-weighted images in axial and sagittal sequences. MRI images show a dilated CSF-filled meningeal sac at the left geniculate ganglia region and dilated labyrinthine segment of the facial nerve canal (Fig. 3 and 4). There is downward displacement of cerebellar vermis by 11 mm below the basion opsithion line (Fig. 4), smooth diffuse pachymeningeal enhancement and distention of dural venous sinuses denoting intracranial hypotension.
Cerebrospinal fluid (CSF) fistula means egression of CSF through an osteodural defect resulting in an abnormal communication between the subarachnoid space and a pneumatised structure in the skull base. CSF leakage from the ear is in the category of perilymphatic fistula. Perilymphatic fistulae may be congenital or acquired. Traumatic, non-traumatic, and spontaneous are the causes of acquired perilymphatic fistula .
Congenital temporal bone CSF fistulae are rare in occurrence and could be perilabyrinthine or translabyrinthine in origin depending on the route of CSF transmission. There are five potential routes of these fistulae: through the tegmen tympani, a large apical air cell, Hyrtl’s fissure, the petromastoid canal and the facial nerve canal . The rare perilabyrinthine group arises from bony defects close to but not including the labyrinth and usually has normal hearing initially. The commoner translabyrinthine group is nearly always accompanied by anacusis, severe labyrinthine dysplasia and a route which communicates between perilymph and the middle ear cavity as through the oval window .
In patients with recurrent meningits, a careful search for abnormal pathway connecting CSF and middle ear cavity is a must.
Bulbous enlargement of geniculate ganglion region on CT examination guiding us to ask for MRI examination, which confirms the nature of this dilatation to be CSF connecting to the internal auditory canal with normal morphological appearance of the cochlea, vestibule and semicircular canals. These imaging findings go with the diagnosis of perilabyrinthine meningocele through the facial nerve canal.
Regarding the management of perilymphatic fistulae, surgery is avoided in those with only hearing loss as the symptoms are unilateral . There have been cases of translabyrinthine fistulae repaired by filling the internal auditory meatus (IAM) with the muscle to stop CSF flowing during stapedectomy . Surgical intervention for serious complication as CSF otorrhoea can be done with surgical repair of the leak with a subtotal petrosectomy or middle fossa craniotomy [5, 6]. In our case report, the patient’s parent preferred a conservative watchful waiting line of treatment.
The presence of continuous ear discharge with recurrent attacks of meningitis should direct attention to the possible risk of CSF fistula, which requires imaging by CT and MRI for determination of the site of origin of this CSF fistula. Early intervention protects the patient from the life-threatening bacterial meningitis.
Written informed patient consent for publication has been obtained.
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