Altered static and dynamic cerebellar-cerebral functional connectivity in acute pontine infarction.

This study investigates abnormalities in cerebellar-cerebral static and dynamic functional connectivity among patients with acute pontine infarction, examining the relationship between these connectivity changes and behavioral dysfunction. Resting-state functional magnetic resonance imaging was utilized to collect data from 45 patients within seven days post-pontine infarction and 34 normal controls. Seed-based static and dynamic functional connectivity analyses identified divergences in cerebellar-cerebral connectivity features between pontine infarction patients and normal controls. Correlations between abnormal functional connectivity features and behavioral scores were explored. Compared to normal controls, left pontine infarction patients exhibited significantly increased static functional connectivity within the executive, affective-limbic, and motor networks. Conversely, right pontine infarction patients demonstrated decreased static functional connectivity in the executive, affective-limbic, and default mode networks, alongside an increase in the executive and motor networks. Decreased temporal variability of dynamic functional connectivity was observed in the executive and default mode networks among left pontine infarction patients. Furthermore, abnormalities in static and dynamic functional connectivity within the executive network correlated with motor and working memory performance in patients. These findings suggest that alterations in cerebellar-cerebral static and dynamic functional connectivity could underpin the behavioral dysfunctions observed in acute pontine infarction patients.

Pons-to-Cerebellum Hypoconnectivity Along the Psychosis Spectrum and Associations With Sensory Prediction and Hallucinations in Schizophrenia.

BACKGROUND: Sensory prediction allows the brain to anticipate and parse incoming self-generated sensory information from externally generated signals. Sensory prediction breakdowns may contribute to perceptual and agency abnormalities in psychosis (hallucinations, delusions). The pons, a central node in a cortico-ponto-cerebellar-thalamo-cortical circuit, is thought to support sensory prediction. Examination of pons connectivity in schizophrenia and its role in sensory prediction abnormalities is lacking. METHODS: We examined these relationships using resting-state functional magnetic resonance imaging and the electroencephalography-based auditory N1 event-related potential in 143 participants with psychotic spectrum disorders (PSPs) (with schizophrenia, schizoaffective disorder, or bipolar disorder); 63 first-degree relatives of individuals with psychosis; 45 people at clinical high risk for psychosis; and 124 unaffected comparison participants. This unique sample allowed examination across the psychosis spectrum and illness trajectory. Seeding from the pons, we extracted average connectivity values from thalamic and cerebellar clusters showing differences between PSPs and unaffected comparison participants. We predicted N1 amplitude attenuation during a vocalization task from pons connectivity and group membership. We correlated participant-level connectivity in PSPs and people at clinical high risk for psychosis with hallucination and delusion severity. RESULTS: Compared to unaffected comparison participants, PSPs showed pons hypoconnectivity to 2 cerebellar clusters, and first-degree relatives of individuals with psychosis showed hypoconnectivity to 1 of these clusters. Pons-to-cerebellum connectivity was positively correlated with N1 attenuation; only PSPs with heightened pons-to-postcentral gyrus connectivity showed this pattern, suggesting a possible compensatory mechanism. Pons-to-cerebellum hypoconnectivity was correlated with greater hallucination severity specifically among PSPs with schizophrenia. CONCLUSIONS: Deficient pons-to-cerebellum connectivity linked sensory prediction network breakdowns with perceptual abnormalities in schizophrenia. Findings highlight shared features and clinical heterogeneity across the psychosis spectrum.

Neurogenic bladder as a lurking complication in Moebius syndrome.

Moebius syndrome (MBS) is a congenital disorder characterized by facial and abducens palsy, sometimes accompanied with other cranial nerve palsies and comorbid conditions. Anatomical anomalies of the brainstem are assumed to be major etiologies of MBS. Its phenotypic presentation can be variable. We report a female patient with MBS who presented with neurogenic bladder (NB). She was born via normal vaginal delivery. At birth, she showed bilateral abducens palsy and right facial palsy. We diagnosed MBS by cranial computed tomography scan and magnetic resonance imaging. She had recurrent urinary tract infection. Hydronephrosis was noted on ultrasonography and bilateral vesicoureteral reflux (grade 5) on voiding cystourethrography. Urodynamic investigation showed detrusor overactivity and detrusor-sphincter dyssynergia, which follow the pattern of NB resulting from infrapontine-suprasacral lesions. Patients with MBS have lower brainstem dysfunction, and accordingly we should be aware of NB.

Longitudinal Changes of Sensorimotor Resting-State Functional Connectivity Differentiate between Patients with Thalamic Infarction and Pontine Infarction.

Purpose. We investigated the disparate influence of lesion location on functional damage and reorganization of the sensorimotor brain network in patients with thalamic infarction and pontine infarction. Methods. Fourteen patients with unilateral infarction of the thalamus and 14 patients with unilateral infarction of the pons underwent longitudinal fMRI measurements and motor functional assessment five times during a 6-month period (<7 days, at 2 weeks, 1 month, 3 months, and 6 months after stroke onset). Twenty-five age- and sex-matched controls underwent MRI examination across five consecutive time points in 6 months. Functional images from patients with left hemisphere lesions were first flipped from the left to the right side. The voxel-wise connectivity analyses between the reference time course of each ROI (the contralateral dorsal lateral putamen (dl-putamen), pons, ventral anterior (VA), and ventral lateral (VL) nuclei of the thalamus) and the time course of each voxel in the sensorimotor area were performed for all five measurements. One-way ANOVA was used to identify between-group differences in functional connectivity (FC) at baseline stage (<7 days after stroke onset), with infarction volume included as a nuisance variable. The family-wise error (FWE) method was used to account for multiple comparison issues using SPM software. Post hoc repeated-measure ANOVA was applied to examine longitudinal FC reorganization. Results. At baseline stage, significant differences were detected between the contralateral VA and ipsilateral postcentral gyrus (cl_VA-ip_postcentral), contralateral VL and ipsilateral precentral gyrus (cl_VL-ip_precentral). Repeated measures ANOVA revealed that the FC change of cl_VA-ip_postcentral differ significantly among the three groups over time. The significant changes of FC between cl_VA and ip_postcentral at different time points in the thalamic infarction group showed that compared with 7 days after stroke onset, there was significantly increased FC of cl_VA-ip_postcentral at 1 month, 3 months, and 6 months after stroke onset. Conclusions. The different patterns of sensorimotor functional damage and reorganization in patients with pontine infarction and thalamic infarction may provide insights into the neural mechanisms underlying functional recovery after stroke.

Motor Organization in Schizencephaly: Outcomes of Transcranial Magnetic Stimulation and Diffusion Tensor Imaging of Motor Tract Projections Correlate with the Different Domains of Hand Function.

OBJECTIVE: Schizencephaly is a rare congenital malformation that causes motor impairment. To determine the treatment strategy, each domain of the motor functions should be appropriately evaluated. We correlated a color map of diffusion tensor imaging (DTI) and transcranial magnetic stimulation (TMS) with the hand function test (HFT) to identify the type of hand function that each test (DTI and TMS) reflects. Further, we attempted to demonstrate the motor neuron organization in schizencephaly. METHOD: This retrospective study was conducted on 12 patients with schizencephaly. TMS was conducted in the first dorsal interosseous (FDI), biceps (BB), and deltoid muscles of the upper extremity, and contralateral MEP (cMEP) and ipsilateral MEP (iMEP) were recorded. The HFT included the grip strength, box and block (B&B), and 9-hole peg test. The schizencephalic cleft was confirmed using magnetic resonance imaging, and the corticospinal tract (CST) was identified using the color map of DTI. The symmetry indices for the peduncle and CST at pons level were calculated as the ratios of the cross-sectional area of the less-affected side and that of the more-affected side. RESULT: In the more-affected hemisphere TMS, no iMEP was obtained. In the less-affected hemisphere TMS, the iMEP response was detected in 9 patients and cMEP in all patients, which was similar to the pattern observed in unilateral lesion. Paretic hand grip strength was strongly correlated with the presence of iMEP (p = 0.044). The symmetry index of the color map of DTI was significantly correlated with the B&B (p = 0.008, R 2 = 0.416), whereas the symmetry index of the peduncle was not correlated with all HFTs. CONCLUSION: In patients with schizencephaly, the iMEP response rate is correlated with the hand function related to strength, while the symmetricity of the CST by the color map of DTI is correlated with the hand function associated with dexterity. Additionally, we suggest the possible motor organization pattern of schizencephaly following interhemispheric competition.

Crossed brainstem syndrome revealing bleeding brainstem cavernous malformation: an illustrative case.

BACKGROUND: Since the nineteenth century, a great variety of crossed brainstem syndromes (CBS) have been described in the medical literature. A CBS typically combines ipsilateral cranial nerves deficits to contralateral long tracts involvement such as hemiparesis or hemianesthesia. Classical CBS seem in fact not to be so clear-cut entities with up to 20% of patients showing different or unnamed combinations of crossed symptoms. In terms of etiologies, acute brainstem infarction predominates but CBS secondary to hemorrhage, neoplasm, abscess, and demyelination have been described. The aim of this study was to assess the proportion of CBS caused by a bleeding episode arising from a brainstem cavernous malformation (BCM) reported in the literature. CASE PRESENTATION: We present the case of a typical Foville syndrome in a 65-year-old man that was caused by a pontine BCM with extralesional bleeding. Following the first bleeding episode, a conservative management was decided but the patient had eventually to be operated on soon after the second bleeding event. DISCUSSION: A literature review was conducted focusing on the five most common CBS (Benedikt, Weber, Foville, Millard-Gubler, Wallenberg) on Medline database from inception to 2020. According to the literature, hemorrhagic BCM account for approximately 7 % of CBS. Microsurgical excision may be indicated after the second bleeding episode but needs to be carefully weighted up against the risks of the surgical procedure and openly discussed with the patient. CONCLUSIONS: In the setting of a CBS, neuroimaging work-up may not infrequently reveal a BCM requiring complex multidisciplinary team management including neurosurgical advice.

Sympathetic hyperactivity, hypertension, and tachycardia induced by stimulation of the ponto-medullary junction in humans.

OBJECTIVE: The purpose of this study is to investigate changes in autonomic activities and systemic circulation generated by surgical manipulation or electrical stimulation to the human brain stem. METHODS: We constructed a system that simultaneously recorded microsurgical field videos and heart rate variability (HRV) that represent autonomic activities. In 20 brain stem surgeries recorded, HRV features and sites of surgical manipulation were analyzed in 19 hypertensive epochs, defined as the periods with transient increases in the blood pressure. We analyzed the period during electrical stimulation to the ponto-medullary junction, performed for the purpose of monitoring a cranial nerve function. RESULTS: In the hypertensive epoch, HRV analysis showed that sympathetic activity predominated over the parasympathetic activity. The hypertensive epoch was more associated with surgical manipulation of the area in the caudal pons or the rostral medulla oblongata compared to controls. During the period of electrical stimulation, there were significant increases in blood pressures and heart rates, accompanied by sympathetic overdrive. CONCLUSIONS: Our results provide physiological evidence that there is an important autonomic center located adjacent to the ponto-medullary junction. SIGNIFICANCE: A large study would reveal a candidate target of neuromodulation for disorders with autonomic imbalances such as drug-resistant hypertension.

Abnormal intrinsic functional network hubs in diabetic retinopathy patients.

BACKGROUND: However, whether the whole-brain functional network hub changes occur in diabetic retinopathy patients remains unknown. PURPOSE: The purpose of the study was to investigate the function network centrality and connectivity changes in diabetic retinopathy patients using the voxel-wise degree centrality method. MATERIALS AND METHODS: Thirty-four diabetic retinopathy patients (18 male and 16 female) and 38 healthy controls (18 male and 20 female) closely matched in age, sex, and education were enrolled in the study. Graph theory-based network analysis was performed to investigate the degree centrality between two groups. RESULTS: Compared with healthy controls, diabetic retinopathy patients had significantly higher degree centrality values in the pons and bilateral caudate and had significantly lower degree centrality values in the left lingual and right lingual, and right angular/middle occipital gyrus (MOG). Moreover, diabetic retinopathy patients exhibited increased functional connectivity between the bilateral lingual and right cerebellum lobe and right fusiform/bilateral caudate and increased functional connectivity between the right angular/MOG and bilateral anterior cingulum and right cuneus/bilateral precuneus and increased functional connectivity between the bilateral caudate and right lingual and right superior occipital gyrus. In contrast, diabetic retinopathy patients showed decreased functional connectivity between bilateral lingual and left lingual and right lingual and left superior occipital gyrus and decreased functional connectivity between the angular/MOG and right inferior occipital gyrus/right fusiform and left MOG/inferior occipital gyrus and decreased functional connectivity between the bilateral caudate and bilateral cerebellum crus1. CONCLUSION: Our results highlight that reorganization of the hierarchy of the cortical connectivity network related to visual network.

Glutamate levels and perfusion in pons during migraine attacks: A 3T MRI study using proton spectroscopy and arterial spin labeling.

Migraine is a complex disorder, involving peripheral and central brain structures, where mechanisms and site of attack initiation are an unresolved puzzle. While abnormal pontine neuronal activation during migraine attacks has been reported, exact implication of this finding is unknown. Evidence suggests an important role of glutamate in migraine, implying a possible association of pontine hyperactivity to increased glutamate levels. Migraine without aura patients were scanned during attacks after calcitonin gene-related peptide and sildenafil in a double-blind, randomized, double-dummy, cross-over design, on two separate study days, by proton magnetic resonance spectroscopy and pseudo-continuous arterial spin labeling at 3T. Headache characteristics were recorded until 24 h after drug administrations. Twenty-six patients were scanned during migraine, yielding a total of 41 attacks. Cerebral blood flow increased in dorsolateral pons, ipsilateral to pain side during attacks, compared to outside attacks (13.6%, p = 0.009). Glutamate levels in the same area remained unchanged during attacks (p = 0.873), while total creatine levels increased (3.5%, p = 0.041). In conclusion, dorsolateral pontine activation during migraine was not associated with higher glutamate levels. However, the concurrently increased total creatine levels may suggest an altered energy metabolism, which should be investigated in future studies to elucidate the role of pons in acute migraine.

Absence of pontine perforators in vertebrobasilar dolichoectasia on ultra-high resolution cone-beam computed tomography.

BACKGROUND: Vertebrobasilar dolichoectasia (VBDE) is a rare type of non-saccular intracranial aneurysm, with poor natural history and limited effective treatment options. Visualizing neurovascular microanatomy in patients with VBDE has not been previously reported, but may yield insight into the pathology, and provide important information for treatment planning. OBJECTIVE: To carry out a retrospective analysis of ultra-high resolution cone-beam computed tomography (UHR-CBCT) in patients with fusiform basilar aneurysms, visualizing neurovascular microanatomy of the posterior circulation with a special focus on the pontine perforators. METHODS: UHR-CBCT was performed in seven patients (mean age 59 years; two female) with a VBDE, and in 14 control patients with unrelated conditions. RESULTS: The mean maximum diameter of the fusiform vessel segment was 28 mm (range 19-36 mm), and the mean length of the segment was 39 mm (range 15-50 mm). In all patients with VBDE, UHR-CBCT demonstrated an absence of perforating arteries in the fusiform arterial segment and a mean of 3.7 perforators arising from the unaffected vessel segment. The network of interconnected superficial circumferential pontine arteries (brainstem vasocorona) were draping around the aneurysm sac. In controls, a mean of 3.6, 2.5, and 1.2 perforators were demonstrated arising from the distal, mid-, and proximal basilar artery, respectively. CONCLUSIONS: The absence of pontine perforators in the fusiform vessel segment of VBDE is counterbalanced by recruitment of collateral flow from pontine perforators arising from the unaffected segment of the basilar artery, as well as collaterals arising from the anterior inferior cerebellar artery/posterior inferior cerebellar artery and superior cerebellar artery. These alternative routes supply the superficial brainstem arteries (brainstem vasocorona) and sustain brainstem viability. Our findings might have implications for further treatment planning.

MRI diffusion and perfusion alterations in the mesencephalon and pons as markers of disease and symptom reversibility in idiopathic normal pressure hydrocephalus.

INTRODUCTION: Core symptomatology in idiopathic normal pressure hydrocephalus (iNPH) points at dysfunction in the mesencephalon and pons indicating pathological changes in these regions, but only a few studies have addressed the issue. The aim of this study was to investigate diffusion (ADC) and perfusion patterns pre- and postoperatively in these areas in iNPH. METHODS: Twenty iNPH patients and 15 healthy controls were included. Patients underwent a clinical examination and brain MRI pre- and 3-6 months postoperatively. The MRI-scan included diffusion and dynamic susceptibility contrast perfusion weighted sequences. Regions of interest in the mesencephalon and pons were drawn on a FLAIR sequence and co-registered to ADC maps and perfusion data. RESULTS: There were no significant differences in pre or postoperative ADC compared to the control group, however postoperative ADC increased by 10% (p = 0.026) in the mesencephalon and 6% (p = 0.016) in the pons in all patients and also in the subgroup of shunt responders by 11% (p = 0.021) and 4% (p = 0.020), respectively. Preoperative relative cerebral blood flow (rCBF) was similar in iNPH patients and controls. Postoperatively, rCBF increased in shunt responders by 6% (p = 0.02) in the mesencephalon and 11% (p = 0.004) in the pons. This increase correlated with the degree of clinical improvement (rs = 0.80, p = 0.031 and rs = 0.66, p = 0.021, respectively). CONCLUSION: The postoperative increase in ADC and the correlation between postoperative increase in rCBF and clinical improvement in the mesencephalon and pons shown in this study point at an involvement of these areas in the core pathophysiology and its reversibility in iNPH.

Abnormal Tuning in Nucleus Prepositus Hypoglossi of Monkeys With "A" Pattern Exotropia.

Purpose: In many individuals with pattern strabismus, the vertical misalignment varies with horizontal eye position. It has been proposed that these cross-axis effects result from abnormal cross-talk between brainstem structures that would normally encode horizontal and vertical eye position and velocity. The nucleus prepositus hypoglossi (NPH) is an ideal structure to test this overarching hypothesis. Neurons in the NPH are believed to mathematically integrate eye velocity signals to generate a tonic signal related to horizontal eye position. We hypothesized that, in monkeys with A-pattern exotropia and vertical inconcomitance, these neurons would show an abnormally large sensitivity to vertical eye position. Methods: Three rhesus monkeys (1 normal and 2 with A-pattern exotropia) were trained to maintain fixation on a visual target as it stepped to various locations on a tangent screen. Extracellular neural activity was recorded from neurons in the NPH. Each neuron's sensitivity to horizontal and vertical eye position was estimated using multiple linear regression and preferred directions computed for each eye. Results: Unexpectedly, the mean preferred directions for the left eye were normal in the monkeys with A-pattern exotropia. For the right eye, there was a clear upward deviation for the right NPH and a downward deviation for the left NPH. In addition, the R2 values were significantly lower for model fits for neurons recorded from the exotropic monkeys. Conclusions: We suggest that vertical inconcomitance results from inappropriate vertical-to-horizontal cross-talk that affects the two eyes differently.

Brain activation patterns of female multiple sclerosis patients with voiding dysfunction.

AIMS: We compared brain activation patterns between female multiple sclerosis (MS) patients with voiding dysfunction (VD) and those without. We aim to expand current knowledge of supraspinal correlates of voiding initiation within a cohort of female MS patients with and without VD. MATERIALS AND METHODS: Twenty-eight ambulatory female MS patients with stable disease and lower urinary tract dysfunction were recruited for this study. Subjects were divided into group 1, without VD (n = 14), and group 2, with VD (n = 14), defined as postvoid residual urine of ≥40% of maximum cystometric capacity or need for self-catheterization. We recorded brain activity via functional magnetic resonance imaging (fMRI) with simultaneous urodynamic testing. Average fMRI activation maps (the Student t test) were created for both groups, and areas of significant activation were identified (P < .05). A priori regions of interest (ROIs), identified by prior meta-analysis to be involved in voiding, were selected. RESULTS: Group-averaged blood-oxygen level-dependent (BOLD) activation maps demonstrated significant differences between groups 1 and 2 during initiation of voiding with group 2 showing significantly lower levels of activation in all ROIs except for the left cerebellum and right cingulate gyrus. Interestingly, group 2 displayed negative BOLD signals, while group 1 displayed positive signals in the right and left pontine micturition center, right periaqueductal gray, left thalamus, and left cingulate gyrus. The activation map of group 1 was similar to healthy controls. CONCLUSIONS: Our results support the hypothesis that distinct supraspinal activation patterns exist between female MS patients with VD and those without.

Altered Spontaneous Activity and Functional Connectivity in the Posterior Pons of Patients With Migraine Without Aura.

The brainstem has been discussed as the main player in the pathogenesis of migraine. Dysfunctional brainstem nuclei and their abnormal connections to other key brain centers may contribute to headache and other symptoms of migraine. In the present study, 32 patients with migraine without aura (MWoA) and 32 age- and sex-matched healthy controls (HCs) underwent resting-state fMRI scans. We used masked independent analysis (mICA) to investigate whether patients with MWoA exhibited abnormal brainstem nuclei-cortical functional connectivity (FC). The mICA can suppress adjacent physiological noise and prevent results from being driven by the much stronger signals of the surrounding structures. Regional homogeneity (ReHo) was used to investigate whether the brainstem regions with abnormal FC to other brain areas exhibited abnormal regional neuronal activity. Patients with MWoA showed significantly weaker FC between the posterior pons and the left superior parietal lobule, the left middle temporal gyrus, and the left middle frontal gyrus. Furthermore, patients with MWoA exhibited significantly decreased ReHo values in the posterior pons compared with HCs, and the posterior pons ReHo value was significantly negatively correlated with HIT-6 scores in the MWoA group. Patients with MWoA exhibited functional abnormalities in the posterior pons and weakened connections between the posterior pons and several key cortical brain areas involved in pain processing during the resting state. PERSPECTIVE: This study provided increased evidence that the pons is involved in the pathophysiological mechanism of migraine, and weakened connections suggest that the touch and pain sensation of migraine sufferers may not be properly relayed to cortical processing areas, which may be associated with the pathogenesis of MWoA.

[«Salt and pepper¼ sign in the onset of a non-vascular pontine pathology]. / Signo de «sal y pimienta¼ como presentacion de una lesion pontina no vascular.

TITLE: Signo de «sal y pimienta¼ como presentacion de una lesion pontina no vascular.

Gentle Perineal Skin Stimulation for Control of Nocturia.

One of the major causes of nocturia is overactive bladder (OAB). Somatic afferent nerve stimuli are used for treating OAB. However, clinical evidence for the efficacy of this treatment is insufficient due to the lack of appropriate control stimuli. Studies on anesthetized animals, which eliminate emotional factors and placebo effects, have demonstrated an influence of somatic stimuli on urinary bladder functions and elucidated the underlying mechanisms. In general, the effects of somatic stimuli are dependent on the modality, location, and physical characteristics of the stimulus. Recently we showed that gentle stimuli applied to the perineal skin using a soft elastomer roller inhibited micturition contractions to a greater extent than a roller with a hard surface. Studies aiming to elucidate the neural mechanisms of gentle stimulation-induced inhibition reported that 1-10 Hz discharges of low-threshold cutaneous mechanoreceptive Aß, Aδ, and C fibers evoked during stimulation with an elastomer roller inhibited the micturition reflex by activating the spinal cord opioid system, thereby reducing both ascending and descending transmission between bladder and pontine micturition center. The present review will provide a brief summary of (1) the effect of somatic electrical stimulation on the micturition reflex, (2) the effect of gentle mechanical skin stimulation on the micturition reflex, (3) the afferent, efferent, and central mechanisms underlying the effects of gentle stimulation, and (4) a translational clinical study demonstrating the efficacy of gentle skin stimuli for treating nocturia in the elderly with OAB by using the two roller types inducing distinct effects on rat micturition contractions. Anat Rec, 302:1824-1836, 2019. © 2019 American Association for Anatomy.

Intraoperative facial motor evoked potential monitoring for pontine cavernous malformation resection.

OBJECTIVE: The aim of this study was to predict postoperative facial nerve function during pontine cavernous malformation surgery by monitoring facial motor evoked potentials (FMEPs). METHODS: From 2008 to 2017, 10 patients with pontine cavernous malformations underwent total resection via the trans-fourth ventricle floor approach with FMEP monitoring. House-Brackmann grades and Karnofsky Performance Scale (KPS) scores were obtained pre- and postoperatively. The surgeries were performed using one of 2 safe entry zones into the brainstem: the suprafacial triangle and infrafacial triangle approaches. Six patients underwent the suprafacial triangle approach, and 4 patients underwent the infrafacial triangle approach. A cranial peg screw electrode was used to deliver electrical stimulation for FMEP by a train of 4 or 5 pulse anodal constant current stimulation. FMEP was recorded from needle electrodes on the ipsilateral facial muscles and monitored throughout surgery by using a threshold-level stimulation method. RESULTS: FMEPs were recorded and analyzed in 8 patients; they were not recorded in 2 patients who had severe preoperative facial palsy and underwent an infrafacial triangle approach. Warning signs appeared in all patients who underwent the suprafacial triangle approach. However, after temporarily stopping the procedures, FMEP findings during surgery showed recovery of the thresholds. FMEPs in patients who underwent the infrafacial triangle approach were stable during the surgery. House-Brackmann grades were unchanged postoperatively in all patients. Postoperative KPS scores improved in 3 patients, decreased in 1, and remained the same in 6 patients. CONCLUSIONS: FMEPs can be used to monitor facial nerve function during surgery for pontine cavernous malformations, especially when the suprafacial triangle approach is performed.