Keywords
occipital dermoid cyst - pediatrics - intracranial abscess - case report
Introduction
Dermoid cysts (DCs) are characterized by a stratified squamous epithelial lining and
differentiated from epidermal cysts by the inclusion of skin adnexa, such as hair
and sebaceous glands, and less frequently, sweat glands, lymphoid tissue, and cartilage.
Lateral brow DCs are the most common type of craniofacial DCs.[1] They usually present as slow-growing asymptomatic masses, located superficially
with no deep extension, and can be managed by direct excisional biopsy. DCs with intracranial
extension in the nasal and frontal regions have been widely reported in the literature.[2]
[3] But an occipital DC with intracranial extension is rare and reported in only nine
children.[4]
[5]
[6]
[7]
[8] We report a rare presentation of an occipital DC with intracranial extension presenting
as a cerebellar abscess with significant cerebellar edema and obstructive hydrocephalus.
The patient had a successful outcome following surgical intervention and antimicrobial
treatment.
Case Presentation
A 2-year-old female child presented to an outside hospital with 3 weeks of worsening
ataxia, emesis, headache, and lethargy. Her head computed tomography (CT) scan ([Fig. 1A]) demonstrated a posterior fossa mass and severe hydrocephalus. Based on these findings
and neurologic deterioration, she was transferred to a tertiary care children's hospital
for neurocritical care and neurosurgical management. In the emergency room, due to
her altered mental status, she was intubated and subsequently underwent brain magnetic
resonance imaging (MRI). The brain MRI revealed a 3.7 × 2.6 cm multiloculated cystic
mass in the right cerebellar hemisphere, causing cerebellar edema and obstructive
hydrocephalus ([Fig. 1B]). On physical examination, she had a small cutaneous lesion with intermittent purulent
drainage in the occipital region ([Fig. 2]) which her mother stated that it had been present since 6 months of age. She was
transferred to the pediatric intensive care unit for initial stabilization with aggressive
medical management of elevated intracranial pressure. She underwent emergency placement
of an externalized ventricular drain (EVD) and suboccipital craniectomy with resection
of the infected dermal sinus tract and a ruptured DC with a large cerebellar abscess.
Fig. 1 Head computed tomography (CT) scan and brain magnetic resonance imaging (MRI) at
the admission and follow-up. (A) Head CT scan demonstrated a posterior fossa mass and severe hydrocephalus. (B) At admission, brain MRI on sagittal T1-weighted sequence with contrast revealed
a 3.7 × 2.6 cm multiloculated cystic mass (white arrow) in the right cerebellar hemisphere.
(C) On postoperative day 7, brain MRI on sagittal T2-weighted sequence without contrast
revealed significant interval improvement in cerebellar edema as well as transependymal
seepage of cerebrospinal fluid (CSF). (D) Prior to discharge, brain MRI on sagittal T1-weighted sequence with contrast demonstrated
increased leptomeningeal enhancement within the surgical bed of the posterior fossa.
(E) At the 5-month follow-up, brain MRI on sagittal T2-weighted sequence without contrast
showed there is no gross new parenchymal signal abnormality, there is no mass effect,
midline shift, or basal cistern effacement, and the cerebellar tonsils terminate above
the foramen magnum.
Fig. 2 A small, cutaneous lesion in the occipital region with intermittent purulent drainage
since 6 months of age.
After surgery, she received vancomycin, which was then narrowed to oxacillin based
on the growth of methicillin-sensitive Staphylococcus aureus from the cerebellar abscess. On postoperative day 7, she was extubated, and she was
alert, awake, and oriented with no focal neurologic deficit with a significant improvement
in cerebellar edema on brain MRI ([Fig. 1C]). On postoperative day 29, the EVD was removed. The patient completed a total of
5 weeks of antimicrobial treatment. Prior to discharge, brain MRI ([Fig. 1D]) demonstrated decreased enhancement adjacent to the suboccipital craniotomy when
compared with the previous study. Her auditory brainstem response monitoring revealed
normal hearing acuity in both ears.
She was seen in the neurosurgery clinic 6 months after discharge. At that time, she
was asymptomatic and there were no concerns for visual impairment. She had no neurological
deficits on the physical examination. The brain MRI ([Fig. 1E]) was reassuring and showed no new parenchymal signal abnormality, mass effect, midline
shift, basal cistern effacement, or abnormal fluid collection.
Discussion
This case represents a rare presentation of an occipital DC in a pediatric patient
with intracranial extension, secondary cerebellar abscess, and hydrocephalus successfully
managed with surgery and antibiotic treatment.
Craniofacial DCs occur in subcutaneous tissues, especially on the face and about the
eyes, and typically appear along lines of facial embryonic fusion. The most common
site is the lateral brow ([Fig. 3]). Uncommon sites include parietal scalp, temporal region, midline nasal, and occipital
region.[1]
[3]
[9] Definitive diagnosis of a DC is important, particularly because DCs in certain locations
have a higher risk of intracranial or intraspinal extension. Only midline nasal, frontal/anterior
fontanelle, and occipital lesions have been associated with intracranial extension.
In one series, 16.3% of occipital DCs had intracranial extension, and 71.4% of these
lesions were identified in the midline.[3] Therefore, presurgical imaging (brain CT or brain MRI) is warranted in patients
with occipital, frontal, and midline nasal DCs.
Fig. 3 Sites of craniofacial dermoid cysts.
Occipital DCs are found in the center of the occipital bone in the midline, where
there is a bony defect through which the dermal sinus extends intracranially. The
natural history of these lesions is often asymptomatic. When symptoms are present,
they include yellow discharge, pain on palpation, swelling, and pruritus.[1] A cutaneous dimple is present at the site of the lesion. In our case, the patient
had a sinus tract at the site with frequent yellow discharge, and this sinus represented
the route of entry for the S. aureus into the cerebellum. To our knowledge, this is the first reported pediatric case
of an occipital DC with intracranial extension and secondary infection.
Imaging studies should be performed for cysts located along the midline, those associated
with any cranial suture, or those with otherwise atypical presentations to delineate
any intracranial or intraspinal extension.[10] The choice of treatment depends on the clinical status and age of the patient, as
well as the size and location of the DCs. Due to the increased risk of epidural and
cerebral expansion of DCs, brain MRI and surgical resection followed by systemic antibiotic
therapy are indicated.[9] Positive outcomes without recurrence are observed in occipital DC after complete
resection.[4]
[5]
[6]
[7]
In conclusion, this case demonstrates a rare presentation of an occipital DC with
intracranial extension and secondary infection and the importance of early imaging
for suspected DCs in the occipital region for identification of intracranial extension.
Adequate preoperative studies are needed to identify any such extension before resection.
Aggressive medical and surgical management of an infected, intracranial lesion is
associated with successful outcomes.
