Outcomes of trigeminal ganglion sparing surgical resection of non-acoustic cerebellopontine angle tumors causing trigeminal neuralgia.

OBJECTIVE: Tumors may be responsible for up to 5% of trigeminal neuralgia (TN) cases. Predictors of long-term pain relief after surgical resection of various cerebellopontine angle (CPA) tumor types are not well understood. Previous studies found that size and extent of resection predict long-term pain status, although resection of tumor involving the trigeminal ganglion (TG) may be associated with high morbidity. This study evaluated predictors of TN pain freedom after resection of a non-acoustic CPA tumor, with avoidance of any portion involving the TG. METHODS: In a retrospective cohort study, we evaluated clinical outcomes and complications after surgical resection of non-acoustic CPA tumors with purposeful avoidance of the TG causing trigeminal neuralgia. The primary outcome was pain-freedom. We performed logistic regression analyses to examine the relationship between pain-freedom at last follow-up and age, side of symptoms, pre-operative symptom duration, tumor diameter, tumor type, and concurrent neurovascular compression (NVC). RESULTS: Of 18 patients with non-acoustic CPA tumors causing TN treated with surgical resection, 83.3% were pain-free at last follow-up (mean 44.6 months). Age(p=0.12), side (p=0.41), pre-operative symptom duration(p=0.85), tumor diameter(p=0.29), tumor type(p=0.37), and NVC presence (p=0.075) were not associated with long-term pain freedom. CONCLUSIONS: This study provides additional evidence that various tumor types causing trigeminal neuralgia may safely undergo surgical resection and decompression of the trigeminal nerve to treat TN. This study presents a cohort of patients that underwent resection of a non-acoustic CPA tumor, with purposeful avoidance of the TG to minimize complications, demonstrating high rates of long-term pain freedom.

Primary central nervous system post-transplant lymphoproliferative disorder after allogeneic stem cell transplantation: a case report.

Purpose: Primary central nervous system, diffuse large B-cell lymphoma, post-transplant lymphoproliferative disorder in the cerebellopontine angle after an allogeneic stem cell transplantation has never been reported in the literature. Typically, diffuse large B-cell lymphoma is non-polyploid. We report the first case of a patient with polyploid post-transplant lymphoproliferative disorder in the cerebellopontine angle who presented with back pain. Case presentation: A 45-year-old man with a history of nodular sclerosing classic Hodgkin lymphoma stage IIB treated with systemic chemotherapy, external radiation and autologous stem cell transplant and double umbilical cord allogeneic transplant presented with several weeks of back pain. He was found to have a small right cerebellopontine angle mass thought to be consistent with a meningioma. Patient presented again two weeks later with acute onset of severe headache, right sided ptosis, right facial numbness, weakness and possible seizure event. Repeat MRI scans showed an interval and significant increase of the right cerebellopontine angle lesion. Biopsy of the cerebellopontine angle lesion was planned with suspicion of lymphoma. Intraoperative pathology consultation findings were not consistent with an acoustic neuroma, meningioma, or epidermoid cyst. Lymphoma could not be definitively identified by intra-operative frozen section. However, it was suspected, and a portion of fresh specimen was submitted for flow cytometry analysis. A near total resection of the tumor and decompression of the brainstem was achieved. Final pathologic analysis was positive for post-transplant lymphoproliferative disorder, monomorphic type, diffuse large B-cell lymphoma, non-germinal center B-cell type, EBV+, post-transplant (allogeneic stem cell) setting (post-transplant lymphoproliferative disorder (PTLD), monomorphic type, diffuse large B-cell lymphoma, non-germinal center B-cell type (non-GCB), EBV-positive under pre-2022 WHO terminology). The patient began a high-dose methotrexate-based regimen (the MATRIX regimen). Conclusions: Our case illustrates an unusual presentation of post-transplant lymphoproliferative disorder in the cerebellopontine angle in a patient with a remote history of allogeneic stem cell transplantation. It demonstrates the importance of keeping primary central nervous system post-transplant lymphoproliferative disorder on the differential for patients who present with back pain or headache that have a history of allogeneic stem cell transplant.

Microvascular decompression for developmental venous anomaly causing hemifacial spasm: illustrative case.

BACKGROUND: Developmental venous anomaly (DVA) is a rare cause of hemifacial spasm (HFS). The treatment of HFS caused by a DVA varies in the literature and includes medication management, botulinum toxin injections, and microvascular decompression (MVD). OBSERVATIONS: A 64-year-old woman presented with right-sided HFS. Preoperative magnetic resonance imaging showed a DVA in the right inferior pons, with an enlarged segment compressing the facial nerve at its root detachment point prior to drainage into the superior petrosal sinus. MVD was performed, and the facial nerve was decompressed without sacrifice of the vein. Immediately following the procedure, the patient had significantly reduced spasms. The patient became spasm-free 3 months after MVD and maintained spasm freedom for 3 months. Six months after MVD, the patient had a partial return of spasms. At 8 months, the patient continued to have reduced and intermittent spasms in the right orbicularis oculi muscle. LESSONS: MVD for HFS caused by a DVA is a safe procedure and can be effective at reducing spasm frequency and severity.

The Sagittal Angle of the Trigeminal Nerve at the Porus Trigeminus is a Radiologic Predictor of Surgical Outcome in Microvascular Decompression for Classical Trigeminal Neuralgia.

BACKGROUND AND OBJECTIVES: Classical trigeminal neuralgia (cTN) is a painful disease. Microvascular decompression (MVD) provides immediate and durable relief in many patients. A variety of positive and negative prognostic biomarkers for MVD have been identified. The sagittal angle of the trigeminal nerve at the porus trigeminus (SATNaPT) is an MRI biomarker that can identify a subset of patients with cTN whose trigeminal nerve anatomy is different from normal controls. The purpose of this case-control study was to determine whether an abnormally hyperacute SATNaPT is a negative prognostic biomarker in patients with cTN undergoing MVD. METHODS: Preoperative MRIs from 300 patients with cTN who underwent MVD were analyzed to identify patients with a hyperacute SATNaPT (defined as less than 3 SDs below the mean). The rate of surgical success (pain-free after at least 12 months) was compared between patients with a hyperacute SATNaPT and all other patients. RESULTS: Patients without a hyperacute SATNaPT had an 82% likelihood of surgical success, whereas patients with a hyperacute SATNaPT had a 58% likelihood of surgical success ( P < .05). Patients with a hyperacute SATNaPT who also had no evidence of vascular compression on preoperative MRI had an even lower likelihood of success (29%, P < .05). CONCLUSION: In patients with cTN being considered for MVD, a hyperacute SATNaPT is a negative prognostic biomarker that predicts a higher likelihood of surgical failure. Patients with a hyperacute SATNaPT, particularly those without MRI evidence of vascular compression, may benefit from other surgical treatments or a modification of MVD to adequately address the underlying cause of cTN.

Minimally invasive surgical evacuation for spontaneous cerebellar hemorrhage: a case series and systematic review.

Spontaneous cerebellar hemorrhage (scICH) is a subset of intracerebral hemorrhage accounting for 5-10% of all cases. Despite potential advantages, minimally invasive surgical evacuation of scICH may be an underutilized strategy when compared to unilateral or bilateral large suboccipital craniectomy or craniotomy, with or without duraplasty. We performed a retrospective single-center cohort study and a systematic literature review. Radiographic and clinical data were recorded and analyzed. Five consecutive patients with minimally invasive surgical evacuation of scICH were identified. Average hematoma size was 16.4 ± 3.0 cm3. Mean Glasgow coma score (GCS) prior to surgery was 11.6 ± 3.0 with improvement to 14.6 ± 0.4 postoperatively. Mean hematoma evacuation was 92.6 ± 0.6% as confirmed by postoperative computed tomography (CT) imaging. All patients achieved a modified Rankin Scale (mRS) score of 0 or 1 with an average follow-up time of 31 ± 22 months. Mean length of hospital stay was 8.8 ± 3.0 days. No patients experienced significant complications or required reoperation. Systematic review revealed similar results for minimally invasive evacuation of scICH when reporting disaggregated outcomes. A review of recent studies utilizing large unilateral or bilateral suboccipital craniectomy or craniotomy, with or without duraplasty, revealed higher morbidity and mortality rates than minimally invasive surgical evacuation of scICH. Minimally invasive evacuation of scICH is safe and effective. Near complete evacuation of hematoma can be achieved with lower morbidity and mortality than large suboccipital craniectomy or craniotomy. A multi-center, prospective, and rigorous trial comparing the two strategies for evacuation of scICH is warranted.

Percutaneous glycerol rhizolysis of the trigeminal ganglion for the treatment of idiopathic and classic trigeminal neuralgia: Outcomes and complications.

BACKGROUND AND PURPOSE: Patients with idiopathic trigeminal neuralgia (TN) with absent arterial contact or venous contact only and classic TN with morphological changes of the trigeminal nerve secondary to venous compression are not routinely recommended microvascular decompression at our institution. In patients with these anatomical subtypes of TN, limited data exists describing the outcomes of percutaneous glycerol rhizolysis (PGR) of the trigeminal ganglion (TG). METHODS: We performed a retrospective single-center cohort study and analyzed outcomes and complications after PGR of the TG. Clinical outcome after PGR of the TG was assessed via the Barrow Neurological Institute (BNI) Pain Scale. RESULTS: Forty-five patients underwent a total of 66 PGRs of the TG. At short-term follow-up, 58 procedures (87.9%) resulted in a BNI score of I (i.e., freedom from pain without medication). At a median follow-up of 3.07 years, 18 procedures (27.3%) resulted in a BNI score of I, 12 procedures (18.1%) resulted in BNI score of IIIa, and 36 procedures (54.5%) resulted in a BNI score of IIIb-V. The median length of freedom from pain without medication was 1.5 years. Eighteen procedures (27.3%) caused hypesthesia and two (3.0%) caused paresthesias. There were no serious complications. CONCLUSION: In patients with these anatomical subtypes of TN there was a high rate of short-term pain relief for the first 1-2 years and thereafter a large proportion of patients experienced pain relapse. In this patient group, PGR of the TG represents a safe procedure that is efficacious in the short term.

Bibliometric Analysis of the Top 100 Cited Articles on Stereotactic Radiosurgery for Trigeminal Neuralgia.

Background Stereotactic radiosurgical rhizolysis of the trigeminal nerve is an established modality increasingly employed to alleviate the symptoms of refractory trigeminal neuralgia. This study analyzes the academic impact of the top 100 cited articles on the radiosurgical management of trigeminal neuralgia. Methods The Scopus database was searched for articles containing "radiosurgery" and one or more of "trigeminal neuralgia," "trigeminus neuralgia," and "tic douloureux." The top 100 articles written in English were arranged in descending order by citation count. Documents were evaluated for authors, publication year, journal and impact factor, total citations, nationality, study type, radiosurgical modality, and the affiliated institution. Quantitative and qualitative analyses were performed on the data. Results The most cited articles were published between 1971 and 2019. The average citation per year was 4.3. The most targeted anatomic area was the "root entry zone" or proximal portion of the cisternal segment of the trigeminal nerve. The most utilized modality was Gamma Knife radiosurgery. The country with the highest number of publications was the United States. Thirty-six percent of the articles were published in the Journal of Neurosurgery . Lunsford, Kondziolka, Flickinger, and Régis, respectively, were the most frequently listed co-authors. The most prolific institute was the University of Pittsburgh Medical Center. Conclusion Stereotactic radiosurgery is an important modality in the management of medically or surgically refractory trigeminal neuralgia. This analysis assesses its contributions over the past five decades to identify trends in treatment practices for neurosurgeons and to highlight areas where further study is needed.

Lateral supraorbital approach for resection of large and giant olfactory groove meningiomas: a single center experience.

BACKGROUND: The lateral supraorbital approach (LSO) provides an optimal access corridor for various skull bases lesions, including olfactory groove meningiomas (OGMs). The aim of this study is to describe the authors' experience with the management of large and giant OGMs utilizing the LSO approach and describe the technical nuances of the procedure. METHODS: A retrospective review of seven patients with large and giant OGMs managed with the LSO approach between 2013 and 2019 was performed. Radiographic and clinical data were recorded and analyzed. RESULTS: Seven patients with large and giant OGMs underwent surgical resection via the LSO approach. Six patients were female, with a median age of 56 years. Patients commonly presented with altered mentation, anosmia, and headaches. The average tumor volume was 120.6 ± 64.7 cm3 with five cases of vascular encasement. Simpson grade II resection was achieved in four patients while Simpson grade IV resection was achieved in three patients. The median length of stay was 2.0 days. The median preoperative Karnofsky Performance Scale (KPS) score was 70, improving to 100 at last postoperative follow-up visit. Two complications were encountered in the form of postoperative cerebrospinal fluid leak in one patient and a transient diplopia in another patient. Tumor recurrence/progression was identified in two patients during a median follow-up time of 65.5 months. Both cases have been managed with adjuvant radiosurgery. CONCLUSION: The LSO approach is a safe and effective minimally invasive transcranial corridor for the management of OGMs that should be part of the armamentarium of skull base neurosurgeons.

Retrosigmoid microvascular decompression as a treatment for trigeminal neuralgia in a patient with osteogenesis imperfecta.

Individuals with osteogenesis imperfecta develop pathologic bone due to genetic defects in collagen synthesis. These patients are prone to skull base abnormalities with resultant lower cranial nerve deficits, most common of which is trigeminal neuralgia. Typically, such patients are managed medically, and surgical options are not well explored for those patients, who become refractory to medication management. While microvascular decompression is often recommended for patients with classical trigeminal neuralgia, neurovascular compression by MRI, and normal skull base anatomy, ablative procedures have been described for patients with trigeminal neuralgia and osteogenesis imperfecta. MVD via a retrosigmoid approach has not been described in a patient with trigeminal neuralgia and skull base abnormalities secondary to osteogenesis imperfecta. A 23-year-old man with osteogenesis imperfecta was referred with right-sided classical trigeminal neuralgia. His trigeminal pain had become refractory to a number of medications. High-resolution MRI demonstrated compression of the trigeminal nerve by the superior cerebellar artery. Microvascular decompression of the trigeminal nerve via a retrosigmoid craniectomy was performed, and he remains pain-free 6 months after surgery. Microvascular decompression of the trigeminal nerve through a retrosigmoid approach can be an effective surgical treatment for young patients with trigeminal neuralgia secondary to osteogenesis imperfecta.

Pain perception genes, asthma, and oral health: A reverse genetics study.

Pain is an experience of a subjective nature, interpreted in a personal way and according to an extensive palette of factors unique to each individual. Orofacial pain can be acute or chronic and it is usually the main reason for the patient to seek dental care. Pain perception varies widely among individuals. This variability is considered a mosaic of factors, which include biopsychosocial factors and genetic factors. Understanding these differences can be extremely beneficial for pain management in a personalized and more efficient way. We performed association studies to investigate phenotypes associated with genetic markers in pain-related genes in two groups of patients who received more or less anesthesia during dental treatment. The study group was comprised of 1289 individuals participating in the Dental Registry and DNA Repository Project (DRDR) of the University of Pittsburgh, with 900 participants in the group that received the most anesthesia and 389 constituting the comparison group that received less anesthesia. We tested 58 phenotypes and genotypic data of seven SNPs in genes that are associated with pain perception, pain modulation and response to drugs used in pain treatment: COMT (rs4818 and rs6269), GCH1 (rs3783641), DRD2 (rs6276), OPRM1 (rs1799971), SCN9A (rs6746030) and SCN10A (rs6795970). The analysis revealed a protective effect of rs1799971 on asthma in the total sample. rs3783641 was associated with salivary secretion disorders in females who received more anesthesia. rs1799971 was also associated with periodontitis in Whites who received less anesthesia. rs4818 was associated with disease and other tongue conditions in the group composed of Blacks who received less anesthesia. In conclusion, our study implicated variants in pain-related genes in asthma and oral phenotypes.

Facial Nerve Massage for the Treatment of Hemifacial Spasm Refractory to Microvascular Decompression: Outcomes and Complications.

BACKGROUND: After microvascular decompression (MVD) for hemifacial spasm (HFS), a minority of patients realize little to no relief of spasms. In some patients, the absence of relief of spasms results from incomplete or inadequate decompression of vascular compression of the facial nerve, and these patients represent excellent candidates for repeat MVD. However, in other patients, repeat MVD is not appropriate because adequate decompression and resolution of neurovascular compression, as determined by postoperative high-resolution MRI, was achieved with the initial operation. OBJECTIVE: To present a cohort of patients with a history of HFS refractory to MVD, with no evidence of neurovascular compression on postoperative MRI, who underwent facial nerve massage (FNM) in the posterior fossa in an attempt to relieve spasms. METHODS: Thirteen patients with a history of incomplete relief of spasms after technically adequate MVD surgery for hemifacial spasm underwent FNM. Immediate and long-term degree of spasm relief and complications after FNM were documented through in-person or telemedicine interview. RESULTS: At follow-up after FNM, 7 of 12 patients (58.3%) reported complete spasm relief (grade I), 2 of 12 patients (16.7%) reported >75% spasm relief (grade II), 0 patient (0%) reported >50% spasm relief (grade III), 3 of 12 (25.0%) patients reported <50% spasm relief (grade IV), and 1 patient was lost to follow-up. One patient experienced a delayed facial paresis, and another patient experienced high-frequency hearing loss. CONCLUSION: After FNM, durable and, at least, partial relief of spasms with a relatively low complication rate was observed in most patients with HFS with incomplete relief of spasms after technically adequate prior MVD.

Direct Pars Repair with Cannulated Screws in Adults: A Case Series and Systematic Literature Review.

OBJECTIVE: Lumbar spondylolysis occurs in 5%-8% of adults. This study aimed to report clinical and radiographic outcomes of direct pars repair in adults with lumbar spondylolysis. METHODS: We conducted a retrospective review of all patients treated for lumbar spondylolysis via open fracture reduction and direct pars repair with cannulated screws using a lag technique. Demographics, clinical presentation, perioperative and intraoperative imaging, and postoperative data were collected. We subsequently performed a systematic review to describe radiographic and clinical outcomes following direct pars repair. RESULTS: Three patients were identified (mean age 40.3 years; range, 21-72 years; 2 male). All patients had bilateral L5 pars fractures treated via open, direct repair with cannulated screws. There were no intraoperative complications. Length of stay was <24 hours for each patient. All patients reported back/radicular symptom relief and returned to full-time manual labor by latest follow-up. Noncontrast lumbar computed tomography performed 14-20 months postoperatively confirmed that all patients had good bilateral screw placement without fracture. Two patients (21 and 28 years old at surgery) had evidence of fusion across fracture sites, while 1 patient exhibited radiolucency around the screws and no progression of spondylolisthesis. Additionally, we reviewed 8210 articles and included 15 in a systematic review of direct pars repair. Fusion rates were 67%-100%, with improved average Oswestry Disability Index and visual analog scale back pain scores by latest follow-up. CONCLUSIONS: Lumbar spondylolysis treatment with open fracture reduction and direct pars repair with cannulated screws in adults is safe and may result in mechanical back/radicular pain relief, even in the absence of radiographic fusion.

Imaging predictors of successful surgical treatment of hemifacial spasm.

Identify preoperative imaging findings in hemifacial spasm patients that predict the post-surgical success following microvascular decompression. This is a retrospective study of patients who were diagnosed with hemifacial spasm, had a dedicated cranial nerve MRI, and underwent microvascular decompression for hemifacial spasm. Bilateral facial nerves were interrogated for neurovascular compression. If neurovascular compression was identified, we recorded whether the offending vessel was an artery, a vein or both. The location of the neurovascular compression (proximal nerve versus distal nerve) was noted. The severity of the neurovascular compression was categorized as contact versus deformity of the nerve. Patients were contacted to determine their post-operative spasm status. The relationships between imaging findings and post-surgical outcome were assessed by Chi-square tests, and odds ratios were calculated to quantify the degree of association. The study included 212 patients. Upon follow up, 192 patients were spasm free (90.57%). Imaging findings on the symptomatic side were as follows: arterial neurovascular compression was seen in 207 patients (97.64%), venous only neurovascular compression in two patients (0.94%), and no neurovascular compression in three patients (1.42%). Arterial neurovascular compression along the proximal, susceptible segment of the nerve was observed in 202 patients (95.28%); deformity was observed more commonly than contact alone. Arterial neurovascular compression along the distal segment only of the nerve was observed in five patients (2.36%). In patients with arterial neurovascular compression of the proximal and distal portions of the nerve, 93.07% and 60.0% of patients were spasm-free respectively. If venous neurovascular compression only was observed on imaging, 0% of patients were spasm-free. Patients with arterial neurovascular compression of the susceptible segment are much more likely to be spasm free than patients without this imaging finding, [odds ratio 20.14 (CI 5.08, 79.81), P-value <0.0001]. When comparing the two groups of arterial neurovascular compression (deformity versus contact), no statistically significant difference in outcomes was observed. In patients with hemifacial spasm undergoing microvascular decompression, imaging findings do predict surgical outcome. Patients with arterial neurovascular compression of the proximal, susceptible portion of the nerve are much more likely to be spasm free after surgery than those without this imaging finding. The imaging findings inform the risk benefit analysis and discussion with patients before they undergo microvascular decompression for hemifacial spasm.

Mechanisms Underlying the Selective Therapeutic Efficacy of Carbamazepine for Attenuation of Trigeminal Nerve Injury Pain.

Different peripheral nerve injuries cause neuropathic pain through distinct mechanisms. Even the site of injury may impact underlying mechanisms, as indicated by the clinical finding that the antiseizure drug carbamazepine (CBZ) relieves pain because of compression injuries of trigeminal but not somatic nerves. We leveraged this observation in the present study hypothesizing that because CBZ blocks voltage-gated sodium channels (VGSCs), its therapeutic selectivity reflects differences between trigeminal and somatic nerves with respect to injury-induced changes in VGSCs. CBZ diminished ongoing and evoked pain behavior in rats with chronic constriction injury (CCI) to the infraorbital nerve (ION) but had minimal effect in rats with sciatic nerve CCI. This difference in behavior was associated with a selective increase in the potency of CBZ-induced inhibition of compound action potentials in the ION, an effect mirrored in human trigeminal versus somatic nerves. The increase in potency was associated with a selective increase in the efficacy of the NaV1.1 channel blocker ICA-121431 and NaV1.1 protein in the ION, but no change in NaV1.1 mRNA in trigeminal ganglia. Importantly, local ICA-121431 administration reversed ION CCI-induced hypersensitivity. Our results suggest a novel therapeutic target for the treatment of trigeminal neuropathic pain.SIGNIFICANCE STATEMENT This study is based on evidence of differences in pain and its treatment depending on whether the pain is above (trigeminal) or below (somatic) the neck, as well as evidence that voltage-gated sodium channels (VGSCs) may contribute to these differences. The focus of the present study was on channels underlying action potential propagation in peripheral nerves. There were differences between somatic and trigeminal nerves in VGSC subtypes underlying action potential propagation both in the absence and presence of injury. Importantly, because the local block of NaV1.1 in the trigeminal nerve reverses nerve injury-induced mechanical hypersensitivity, the selective upregulation of NaV1.1 in trigeminal nerves suggests a novel therapeutic target for the treatment of pain associated with trigeminal nerve injury.

Prevalence and severity of neurovascular compression in hemifacial spasm patients.

Hemifacial spasm is typically caused by vascular compression of the proximal intracranial facial nerve. Although the prevalence of neurovascular compression has been investigated in a cohort of patients with classical trigeminal neuralgia, the prevalence and severity of neurovascular compression has not been well characterized in patients with hemifacial spasm. We aimed to investigate whether presence and severity of neurovascular compression are correlated to the symptomatic side in patients with hemifacial spasm. All patients in our study were evaluated by a physician who specializes in the management of cranial nerve disorders. Once hemifacial spasm was diagnosed on physical exam, the patient underwent a dedicated cranial nerve protocol magnetic resonance imaging study on a 3 T scanner. Exams were retrospectively reviewed by a neuroradiologist blinded to the symptomatic side. The presence, severity, vessel type, and location of neurovascular compression along the facial nerve was recorded. Neurovascular compression was graded as contact alone (vessel touching the facial nerve) versus deformity (indentation or deviation of the nerve by the culprit vessel). A total of 330 patients with hemifacial spasm were included. The majority (232) were female while the minority (98) were male. The average age was 55.7 years. Neurovascular compression (arterial) was identified on both the symptomatic (97.88%) and asymptomatic sides (38.79%) frequently. Neurovascular compression from an artery along the susceptible/proximal portion of the nerve was much more common on the symptomatic side (96.36%) than on the asymptomatic side (12.73%), odds ratio = 93.00, P < 0.0001. When we assessed severity of arterial compression, the more severe form of neurovascular compression, deformity, was noted on the symptomatic side (70.3%) much more frequently than on the asymptomatic side (1.82%) (odds ratio = 114.00 P < 0.0001). We conclude that neurovascular compression that results in deformity of the susceptible portion of the facial nerve is highly associated with the symptomatic side in hemifacial spasm.