Emotional Lability as a Symptom of Extra-axial Posterior Fossa Tumors: A Case-Control Review of Neuroanatomy and Patient-Reported Quality of Life

Introduction: Emotional lability (EL), the uncontrollable and unmotivated expression of emotion, is a rare and distressing symptom of brainstem compression from extra-axial posterior fossa tumors. In all published case reports, EL is alleviated by surgical resection of the tumor. The primary goal of this study was to radiographically compare the degree of compression from mass lesions onto brainstem structures between EL cases and matched controls. We hypothesized that distortion of brainstem nuclei by mass lesions specifically in the basis pontis region causes EL. Because EL can be a significant social and professional burden, the secondary goal of the study was to compare acute changes in quality of life (QOL) survey scores pre- and postoperatively. We hypothesized that postoperative QOL improvements for patients with EL would be greater than those of matched non-EL control patients.

Methods: In a retrospective review of 673 patients treated for posterior fossa tumors with brainstem compression between 2002 and 2018 at Vancouver General Hospital, 11 patients with confirmed EL were identified. Each case was matched to three controls for tumor pathology, general tumor location, and time of surgical treatment (±2 years). Cases and controls were homogeneously treated by the same fellowship-trained skull base neurosurgeon.

Neuroanatomy: Preoperative axial T2-weighted MRI scans were reviewed and a lateral brainstem compression scale ([Fig. 1]) was used to characterize the degree of mass effect at the level of the medulla, pons, and midbrain. Compression scale scores were compared between EL patients and control patients to identify which brainstem regions are implicated in the EL pathway. Variables including gender, age, handedness, tumor laterality, and tumor size were also compared.

QOL: Patients complete SF-36v1 surveys at clinic visits as standard of care. Preoperative and postoperative surveys were retrospectively obtained from patient charts. Gender, age, total survey scores, and survey subscores were compared.

Results: EL symptoms ceased postoperatively for all patients. A binomial logistic regression found that compared with the control group, EL-causing tumors occurred in younger patients (EL mean age = 38.1 years, control mean age = 51.3 years, two-tailed p = 0.04) and EL tumors exert greater compression onto the pons (EL mean compression score = 2.91, control mean compression score = 1.91, one-tailed p = 0.03). A linear mixed-effects model found that patients with EL-causing tumors experience greater improvement postoperatively in the “Role Limitations Due to Physical Health” (two-tailed p = 0.02) and “Overall Health Change” (two-tailed p = 0.04) sub-scores. Other tested variables remained consistent between groups.

Conclusion: This is the largest case series to date on adult extra-axial posterior fossa tumors that cause EL. The neuroanatomy results suggest that compression onto the pons inhibits control over involuntary, stereotyped expression of emotion. This study adds to the body of evidence that EL may be attributed to deafferentation of the cerebellum from cortical and limbic structures through the basis pontis, leading to impaired modulation of emotional response. The QOL results suggest that increased improvement for EL patients in the “Role Limitations Due to Physical Health” and “Overall Health Change” QOL subcategories augments the benefits of obtaining EL-alleviating surgery.