CASE 1367 Published on 27.12.2001

Cerebellar abscess secondary to dermal sinus tract

Section

Neuroradiology

Case Type

Clinical Cases

Authors

J.R.Torino, R.Puy, J.Blanch, E.Sainz*, V.Cusí**

Patient

12 months, female

Categories
No Area of Interest ; Imaging Technique Ultrasound, CT, MR
Clinical History
The patient was admitted with somnolence, irritability and fever. CSF analysis showed increased WBC and RBC counts and increased protein level. Imaging revealed a mass effect in the cerebellar area.
Imaging Findings
The patient was admitted to the emergency department with somnolence, irritability, anorexia and fever in the past 48 hours. CSF analysis after lumbar puncture showed an increased white blood cell count, red blood cell count and protein level.

Ultrasonography, CT and MRI of the cranium were performed, and revealed a cerebellar mass suggestive of an abscess with an adjacent daughter abscess and with associated obstructive hydrocephalus.

Physical examination demonstrated an occipital dermal sinus. At surgery the dermal sinus communicated with the abscess through a tract. Histological examination demonstrated the abscess and the dermal sinus.

Discussion
Cerebellar abscesses are localised purulent collections inside the cerebellum. They may be related to meningeal infection or open directly to the fourth ventricle. They start out as localised or disseminated cerebritis that ends up being enveloped by a glioconjunctival capsule, inducing intense surrounding oedema that may lead to compression of neighboring structures.

The most frequent cause of cerebellar abscess is local extension from an otic infection. Less frequent causes include paranasal infections; disseminated infections originating in the heart, lung or bone; trauma or surgery; immune deficiencies, etc. Up to 25% of cerebellar abscesses are of unknown cause (1).

As this case in childhood illustrates, with a posterior fossa abscess and no associated cause, the presence of an occipital dermal sinus should be investigated, always looking for the characteristic skin stigma and underlying bone defect (2).

The dermal sinus is a thin epithelial tube extending from the occipital dermis into intracranial structures, being the consequence of a failure in closing of the neuropore during embryogenesis, around the fourth week of gestation. During neuroectodermic migration, the mesoderm remains interposed during closure of the middle line (3).

CT scan and MRI are very sensitive techniques to detect and characterise this lesion. Both techniques show a single or multiple cystic mass, with annular contrast enhancement, and local oedema (2,3). MRI has the advantage of better spatial resolution and higher sensitivity in studying the posterior fossa. However, the presence of a small dermal sinus is easily detected with CT because of its better bone definition. Besides allowing for the localisation of the lesion, both techniques may occasionally point towards the primary septic origin and are mandatory for the follow-up of surgical and medical treatment (1,2,3).

Differential Diagnosis List
Cerebellar abscess secondary to dermal sinus tract
Final Diagnosis
Cerebellar abscess secondary to dermal sinus tract
Case information
URL: https://www.eurorad.org/case/1367
DOI: 10.1594/EURORAD/CASE.1367
ISSN: 1563-4086