A 42-year-old Hispanic woman, who had a history of a left-sided temporal mass, arrived at the emergency department following a new-onset and witnessed a tonic-clonic seizure. Doctors managed the seizures with the administration of 4 mg midazolam intravenously. She underwent endotracheal intubation for airway protection. Remarkably, she had been carrying this temporal cystic subcutaneous mass since adolescence without any intervention.
The initial imaging studies included a computer tomography (CT) scan and a magnetic resonance imaging (MRI) scan of the brain. This revealed a left frontotemporal tumour with fat density. This tumour was associated with bone scalloping and a suspected partial rupture into the surrounding subarachnoid space. Doctors noticed hyperintensities, likely indicating the presence of associated fat droplets.
Subsequently, she underwent a left-sided craniotomy and craniectomy the next day for the resection of two separate masses. The surgical procedure included the use of titanium mesh cranioplasty.
During the surgery, doctors discovered that there were two distinct tumours eroding through the skull. They had unclear origins, whether intracranial or extracranial. They successfully resected the posterior tumour, while debulking the anterior tumour. This was due to a portion of the tumour capsule being adherent to the brain tissue and causing bleeding during a further removal attempt. The bleeding was attributed to its involvement with the vein of Labbe and several branches of the middle cerebral artery (MCA).
Pathological examination of the masses confirmed the presence of a mature teratoma or dermoid cyst with associated fat necrosis. Multiple tissues were identified, including hair follicles, sebaceous glands, and keratin. The doctors discharged the patient on the seventh day with a prednisone taper.
The patient was lost to follow-up after discharge, making it challenging to monitor her progress and provide ongoing care.
A dermoid cyst is a mass that emerges between the third and fifth weeks of embryonic development, resulting from the abnormal migration of ectodermally originated cells. These cells include hair follicles, sweat glands, and sebaceous glands during neural tube closure. This leads to the formation of a microcystic mass in an atypical location. These cysts, which can originate intracranially or extracranially, typically exhibit a benign and slow-growing nature. This is due to the physiological activity of their internal dermal components. Intracranial dermoid cysts (IDCs) are rare, constituting < 1% of all intracranial lesions, and often appear in the first four decades of life. Common locations for IDCs include midline in the posterior fossa, midline/para-sellar, frontal, and intradural regions.
While IDCs are mostly asymptomatic, patients may manifest symptoms resulting from mass effects or irritation. These symptoms include headaches, seizures, olfactory hallucinations, cranial nerve compression, and hydrocephalus. Symptoms typically arise between the ages of 16 and 60, with an average onset age of 32. Spontaneous rupture of IDCs, though rare, can lead to severe complications like headaches, seizures, damage to neurovascular structures, sensory or motor deficits, chemical meningitis, vasospasm, cerebral ischemia, and even death due to the dissemination of cyst contents. The precise pathophysiology of IDC rupture remains poorly understood, with hypotheses suggesting glandular secretions, age-dependent hormones, spontaneous rupture, trauma, surgery, and head movements as potential triggers.
Extracranial dermoid cysts (EDCs), also known as scalp dermoids, share similar contents with IDCs but develop extracranially during childhood, with an incidence of 20%. Although mostly asymptomatic, they may present as a subcutaneous asymptomatic mass. The preferred treatment for EDCs is complete surgical excision, as untreated cases may risk bony erosion with intracranial expansion, exposing patients to similar risks as IDCs. Subcutaneous sinus tracts and extensions to the subcutaneous space, mimicking extracranial dermoid cysts infiltrating the intracranial space, have been observed in IDCs.
In this case of dermoid cyst, the patient, in her fifth decade, makes it challenging to find the original mass’s nature. It is inferred that, due to the prolonged course of her disease and the late onset of complications, the initial lesion was an EDC with intracranial expansion, culminating in rupture. Brain imaging findings, classic for both IDCs and EDCs, did not permit a definitive classification. The neurosurgeon couldn’t determine whether the cysts originated intracranially or extracranially. Unlike extracranial dermoid cysts, current recommendations for treating IDCs involve conservative management until symptoms arise. However, this poses risks such as malignant transformation, hydrocephalus, cutaneous sinus tract development, recurrent bacterial meningitis, or rupture if left untreated.
Conclusion: Cause of Dermoid Cyst Rupture
The patient’s rupture appears to have happened spontaneously, with no identifiable cause. It is suspected that the rupture and content dissemination caused the seizures. Although the patient presented with classic post-rupture seizure symptoms, her only prior sign was the cystic mass as a child, with no previous loss of consciousness, vision loss, focal neurological deficits, or seizures. The initial evaluation at 15 years of age for an asymptomatic mass on the left temple occurred over 10 years later than the average presentation age. Considering this initial mass as an EDC, it had a 37–57% chance of intracranial extension, exposing the patient to similar complications. Malignant transformation is a critical sequela, although rare. Despite the absence of malignancy in pathology, future development cannot be ruled out, requiring long-term, close follow-up.