Dermoid Cyst Causing Neonatal Brain Abscesses: A Case Report

Introduction

Brain abscess is a rare and life-threatening central nervous system infection, which is relatively uncommon in pediatric patients [1]. It is typically associated with conditions such as sinusitis, otitis media, dermoid cysts, or head trauma, and is even rarer in neonates, with the most common causes being meningitis and septicemia. Dermoid cysts (DCs) are relatively rare benign tumors, accounting for 0.025% to 0.04% of all intracranial tumors. These cysts can become infected or rupture, leading to complications such as headaches, seizures, chemical meningitis, neurological deficits, or hydrocephalus.

Case Report

A 2-month-old male infant, born prematurely at 28+4 weeks’ gestation, was admitted to the Intensive Care Unit (ICU) in July 2024 due to a half-day history of feeding refusal and moaning. His past medical history was significant for threatened preterm labor and intrauterine infection. Following admission, his condition deteriorated rapidly, manifesting as apnea, altered consciousness, weak spontaneous respirations, and blood gas analysis indicative of respiratory failure. He received invasive mechanical ventilation, dobutamine for inotropic support, phenobarbital sodium and midazolam for seizure control, and meropenem for anti-infective therapy. Physical examination revealed poor responsiveness, a sallow-gray complexion, dyspnea, and a flat, soft anterior fontanelle. Positive suprasternal, intercostal, and subcostal retractions (three-concave sign) were noted. Auscultation revealed coarse breath sounds bilaterally with audible moist rales, more pronounced in the right lung.

Abnormal laboratory values were white blood cell (WBC) count 4.12×109/L, platelet count 64.00×109/L, neutrophil percentage 73.60%, and C-reactive protein (CRP) 138.99 mg/L. CSF cell count showed WBCs 1419.00×106/L and polymorphonuclear cells 645.00×106/L. Blood culture grew gram-negative bacilli. Initial cranial ultrasound and magnetic resonance imaging (MRI) revealed no significant abnormalities.

Diagnosis: The neonate was diagnosed with neonatal sepsis, neonatal purulent meningitis, neonatal pneumonia, septic shock, neonatal respiratory failure, cardiac insufficiency, neonatal convulsions, neonatal thrombocytopenia, and neonatal apnea.

After 11 days of treatment, physical examination revealed mild swelling and redness in the posterior fontanelle area at the midline and slightly to the left of the occipitoparietal region, approximately 3 cm in diameter, soft in texture, with slight fluctuation. The brain enhanced MRI showed abnormal enhancement signals in the right parietal lobe and the left parieto-occipital area, suggesting an infectious lesion. Brain tissue compression and midline shift were observed (Figure 1). Given that the infection of the dermoid cyst was identified as the underlying cause of the purulent meningitis and considering the significant brain tissue compression due to the large abscess, conservative treatment was determined to be relatively ineffective. Consequently, we proceeded with endotracheal intubation general anesthesia to perform a brain abscess excision and drainage, combined with subdural effusion external drainage surgery. During the operation, a cyst infection was observed, and it had eroded the underlying dura mater, with tight adhesion between the cyst wall, brain tissue, and dura mater surrounding the dura mater, thickening of the dura mater, and necrosis of the surrounding brain tissue. The infected cyst wall was separated from the surrounding dura mater, carefully dissected from the lateral to the midline to the brain tissue interface, with protection of the sagittal sinus at the midline, and deep erosion of the falx cerebri. The infected cyst had broken through to the opposite side. The right dura mater was incised, and the infected cyst and necrotic brain tissue were thoroughly removed, connecting both sides. The skull defect was about 1x3 cm in size (Figure 2). Infected DSTs and ruptured DCs with parieto-occipital brain abscess were resected (Figure 3). Postoperative pathological examination showed that purulent inflammation with abscess formation was formed. After surgery, the child was treated with meropenem (0.2 g Q8H 21 d) and linezolid (0.05 g Q8H 21 d) to resist infection. The child recovered smoothly after surgery, and follow-up showed good growth, with no recurrence or neurological sequelae (Figures 4, 5).

Discussion

Dermoid Cysts are congenital developmental anomalies characterized by stratified squamous epithelial lining containing skin appendages (such as hair and sebaceous glands), and occasionally sweat glands, lymphoid tissue, and cartilage. Craniofacial dermoid cysts account for approximately 7% of all dermoid cysts, with an incidence rate between 0.03% and 0.14% [2]Clinically, DCs often present insidiously, manifesting as fistulas, hemangiomas, or subcutaneous masses. Clinical symptoms typically include swelling, abnormal secretions, pain, and pruritus [3,4]. This report presents a rare case of vertex DCs, which was particularly challenging to diagnose as the initial physical examination revealed no subcutaneous mass or skin inflammation, making it exceptionally occult.

Once infected, skin microorganisms can enter the cyst through sinus tracts, leading to suppuration within the cyst, enlargement, and rupture. The cyst contents may then be released into the ventricular system and subarachnoid space, spreading to the leptomeninges and causing purulent meningitis, which can result in complications such as sepsis, brain abscess, and hydrocephalus [3,5–7]. The main pathogenic organisms include Staphylococcus aureus, gram-negative bacilli, and anaerobic bacteria. In this case, gram-negative bacteria were identified in blood culture, likely associated with post-cyst infection sepsis. No bacterial growth was observed in the intraoperative pus culture, possibly due to prior sensitive antibiotic administration and culture condition limitations.

Neonatal brain abscesses can result from bacterial, fungal, or viral infections causing meningitis and sepsis [8]. Neonates with brain abscesses face a higher mortality risk, and survivors may experience permanent damage such as hemiplegia, epilepsy, and cognitive impairment [9]. Symptoms and signs in neonates and infants can be non-specific and misleading. Clinical manifestations typically include fever, feeding refusal, irritability, lethargy, convulsions, and vomiting [10]. Due to the anatomical characteristics of open fontanelles and sutures in neonates, specific clinical manifestations like increased intracranial pressure may be absent, making the condition occult and prone to missed or delayed diagnosis. In this case, the patient showed no fever, sutural diastasis, or increased fontanelle tension, and the rapid disease progression was inconsistent with typical clinical presentations of brain abscess secondary to purulent meningitis. Therefore, in such pediatric patients, after ruling out other conditions presenting with similar signs and symptoms, early cerebrospinal fluid examination is recommended. If abnormalities are detected, neuroimaging should be promptly performed.

The diagnosis of brain abscess can be made through cranial CT or MRI. CT scans are more effective for older children because the high water content in the brains of newborns reduces the contrast between normal and affected tissues [11]. Enhanced MRI is the best method to prove the specific and non-specific expressions of intracerebral infectious inflammatory reactions, as it can more accurately determine the extended range of sinus tract extension and its relationship with abscesses, cysts, and venous structures. This imaging assessment is vital for early diagnosis and timely intervention. MRI typically shows ring-enhancing lesions on T1 scans after injecting contrast agents, and the DWI is shown on central high signal, with corresponding low ADC values. Dermoid cysts present as high signal on T1WI, and their signals on T22WI are variable, also showing high signal on DWI. Reviewing this patient’s cranial MRI at 1 month of age and comparing the same DWI plane at age 2 months, the high signal observed at 1 month was likely a dermoid cyst that could be easily overlooked clinically. Therefore, we believe that for lesions, especially those near the midline, further neuroradiological examination is necessary to exclude potential dermoid sinus tracts (DSTs) and DCs.

Bodilsen et al recommend that all patients undergo neurosurgical aspiration or brain abscess excision as soon as possible, if feasible (except for toxoplasmosis) [11]. Infection of a dermoid cyst is often the primary source of central nervous system infection and a key reason for treatment failure; we advocate for early surgical intervention. The goal is complete excision of the mass and sinus tract. While complete abscess drainage is ideal, it can be challenging if the cyst capsule is densely adhered to vital adjacent structures, such as venous sinuses. In such cases, subdural and subcutaneous drains are placed for layered and thorough drainage, followed by standardized postoperative antibiotic therapy. Some patients develop complications like subdural effusion or post-infectious hydrocephalus. These require close postoperative follow-up with regular imaging, adequate anti-infective treatment, and, potentially, further surgical intervention once the infection is controlled.

Conclusions

This case report describes a rare presentation of a neonatal dermoid cyst (DC) with intracranial extension and subsequent secondary infection. When evaluating intracranial lesions resulting from central nervous system infections, the possibility of underlying dermoid cysts and associated sinus tracts must be considered. This underscores the importance of thorough physical examination and early imaging in suspected cases of DCs. Once diagnosed, prompt and aggressive surgical intervention is crucial, aiming for maximal lesion resection and layered drainage.