Abstract
BACKGROUND
Trigeminal schwannomas are rare intracranial tumors that predominantly occur in adults and only exceptionally present in the pediatric population. Behavioral disturbances, particularly pathological laughter and impulsive dysregulation, are uncommon neurological manifestations and typically indicate disruption of supranuclear or brainstem networks by an underlying structural lesion. Their association with trigeminal schwannoma remains exceedingly rare and poorly characterized.
OBSERVATIONS
A 13-year-old boy presented with progressive behavioral disturbances, including pathological laughter, impulsivity, and agitation, along with focal neurological deficits in the form of hemiparesis. Neuroimaging revealed a giant trigeminal schwannoma with extension into the cerebellopontine angle and adjacent compartments, exerting significant mass effect on the brainstem and surrounding neural structures. The patient underwent surgical intervention with the aim of maximal safe resection. Postoperatively, there was improvement in both neurological deficits and behavioral symptoms, supporting a structural basis for the observed neuropsychiatric manifestations.
LESSONS
This case highlights an unusual presentation of trigeminal schwannoma in a pediatric patient, manifesting predominantly with behavioral dysregulation. It underscores the importance of considering structural intracranial lesions in children presenting with atypical behavioral symptoms. Recognition of such manifestations has important implications for early diagnosis, surgical planning, and prognostication, and further supports a network-based understanding of affective and behavioral control.
Keywords: trigeminal schwannoma, pediatric schwannoma, pathological laughter, case report
Trigeminal schwannomas are rare intracranial tumors, accounting for approximately 0.07%–0.3% of all intracranial neoplasms and 0.8%–5% of intracranial schwannomas.1–3 These tumors are typically diagnosed in adults in their 4th and 5th decades, while pediatric cases are uncommon and may present with atypical features. Behavioral disturbances, particularly pathological laughter and impulsive dysregulation, are uncommon neurological manifestations and typically indicate disruption of supranuclear or brainstem networks by an underlying structural lesion. Their association with trigeminal schwannoma remains exceedingly rare and poorly characterized.
We describe a rare pediatric case of trigeminal schwannoma with distinctive clinical and radiological features, presenting with prominent behavioral disturbances, including pathological laughter, impulsivity, agitation, and hemiparesis. To the best of our knowledge, no pediatric case of trigeminal schwannoma manifesting with behavioral disturbance has been reported in the literature to date.
Illustrative Case
A 13-year-old boy presented with a 6-month history of progressive right-sided hemiparesis, accompanied by dysarthria, headache, and dysphagia. His caregivers also reported behavioral changes, including aggression, impulsivity, hyperexcitability, and reduced sleep.
He experienced recurrent, brief paroxysmal episodes of sudden, inappropriate laughter without identifiable triggers. These episodes were not associated with altered consciousness, postictal confusion, or automatism. There was no prior neurological or psychiatric history.
On examination, higher mental functions were preserved. Cranial nerve evaluation revealed right-sided lower motor neuron facial weakness (House-Brackmann grade II) and decreased sensation across all divisions of the right trigeminal nerve. Right gaze-evoked nystagmus was present, and audiometry showed minimal right-sided sensorineural hearing loss. The uvula deviated to the left with a diminished gag reflex on the right, suggesting involvement of the glossopharyngeal and vagus nerves.
Cerebellar examination demonstrated right-sided limb ataxia and dysdiadochokinesia. Motor examination showed right hemiparesis with Medical Research Council grade 4/5 and reduced grip strength.
Evaluation for neurofibromatosis revealed no contributory findings.
MRI demonstrated a large dumbbell-shaped extra-axial lesion in the right cerebellopontine angle extending into Meckel’s cave (5.1 × 4.7 × 3.3 cm), with mixed cystic and solid components. The lesion was iso- to hypointense on T1-weighted images and heterogeneously hyperintense on T2-weighted images. Postcontrast imaging showed a predominantly nonenhancing cystic component with an eccentrically enhancing solid nodule situated within Meckel’s cave. The tumor extended into the cavernous sinus with partial encasement of the internal carotid artery, with preserved luminal patency. Significant brainstem compression was noted. (Fig. 1A–C)
FIG. 1.
Preoperative axial (A), coronal (B), and sagittal (C) T1-weighted contrast-enhanced images demonstrating a large nonenhancing cystic lesion with an eccentrically enhancing solid component in Meckel’s cave, causing brainstem compression. Postoperative axial (D), coronal (E), and sagittal (F) images showing a heterogeneously enhancing residual lesion in the right Meckel’s cave extending to the posterior aspect of the right cavernous sinus.
Trigeminal schwannoma was diagnosed based on clinical and radiological findings. Given that the tumor bulk was predominantly located in the right cerebellopontine angle, with limited extension into Meckel’s cave, a right retrosigmoid suboccipital craniotomy with suprameatal extension was performed to excise the tumor.
Intraoperatively, the tumor was a soft, grayish-white, extra-axial mass arising from the trigeminal nerve with a clear cleavage plane. Cranial nerves III, IV, VI, VII, and VIII were preserved. Internal decompression revealed a cystic component and tumor extension into Meckel’s cave, and the petrous apex was excised. Endoscopic assistance ensured maximal safe resection.
Histopathological analysis confirmed a World Health Organization grade I schwannoma.
Postoperatively, the patient developed transient worsening of facial nerve paresis, which improved over time. Hypoesthesia in the trigeminal distribution persisted. Lower cranial nerve dysfunction caused dysphagia, requiring temporary enteral feeding, with gradual recovery.
Cerebellar signs improved significantly. Notably, the pathological laughter and behavioral disturbances resolved completely within 2 months. Motor function improved progressively, with near-complete recovery.
Three-month postoperative contrast-enhanced MRI (Fig. 1D–F) revealed a residual enhancing lesion within Meckel’s cave, for which the patient was planned for adjuvant radiotherapy.4
Informed Consent
The necessary informed consent was obtained in this study.
Discussion
Observations
Pathological laughter represents a disorder of affective expression caused by disruption of supranuclear control mechanisms. It is associated with lesions involving the cortex, diencephalon, or brainstem, reflecting dysfunction of integrated motor-emotional networks.
Affective expression is regulated by two interconnected systems: the corticobulbar pathway, responsible for voluntary facial movement, and the fronto-ponto-medullary pathway, which governs emotional expression.5 Higher cortical centers normally exert inhibitory control over brainstem circuits, ensuring appropriate emotional responses. Disruption of these pathways leads to dissociation between emotional experience and expression, resulting in inappropriate affect.5 Reports of pathological laughter in other pediatric brainstem tumors, most notably diffuse intrinsic pontine glioma, lend further support to the hypothesis that interruption of the cerebro-ponto-cerebellar network constitutes the principal mechanism responsible for this behavioral manifestation.6,7
In trigeminal schwannomas, particularly those extending into the cerebellopontine angle and brainstem, behavioral disturbances may arise due to mass effect on adjacent neural structures. Brainstem compression can disrupt pathways mediating emotional expression, while involvement of thalamic and frontotemporal connections may impair higher-order regulation.
Behavioral dysregulation may also result from disruption of fronto-limbic circuits. The orbitofrontal cortex and anterior cingulate cortex play key roles in inhibitory control and emotional regulation through modulation of limbic structures such as the amygdala.8 Disturbance of these pathways may manifest as impulsivity, aggression, and disinhibition.
Recognition of such behavioral symptoms as manifestations of structural lesions is critical, as they may aid in localization and reflect functional network disruption. Importantly, surgical decompression can restore neural pathway integrity, leading to resolution of symptoms. Thus, this report highlights the importance of considering intracranial structural lesions in children presenting with atypical neuropsychiatric manifestations. Moreover, the detailed clinicoradiological correlation, operative findings, and postoperative resolution of behavioral symptoms provide indirect evidence supporting a structural network-based mechanism involving brainstem and fronto-limbic pathways. However, as a single case observation, causal relationships between tumor location and behavioral manifestations cannot be established definitively. Nevertheless, the temporal association between surgical decompression and complete resolution of behavioral symptoms strongly supports a reversible network dysfunction rather than a primary psychiatric disorder.
Lessons
Pediatric trigeminal schwannomas are rare and may present with atypical neurobehavioral symptoms, including pathological laughter and behavioral dysregulation, warranting evaluation for underlying structural lesions.
Postoperative resolution of these abnormalities supports reversible supranuclear dysfunction and emphasizes the value of timely surgical intervention for optimal outcomes.
Disclosures
The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
Author Contributions
Conception and design: both authors. Analysis and interpretation of data: Sharma. Drafting the article: Shukla. Critically revising the article: both authors. Reviewed submitted version of manuscript: both authors. Approved the final version of the manuscript on behalf of both authors: Shukla.
Correspondence
Vigya Shukla: All India Institute of Medical Sciences, Raipur, Chhattisgarh, India. vigya.tiny92@gmail.com.
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