Use of Ultra-Short Echo Time MRI to Improve Temporal Bone Imaging.

OBJECTIVE: The short T2 nature of cortical bone causes it to appear similar to air on MR, forcing clinicians to rely on computed tomography imaging, with its attendant ionizing radiation exposure, to define temporal bone structures. Through the use of novel MR sequences with ultra-short echo times (UTE), short T2 structures are now able to be visualized, allowing for improved understanding of anatomical relationships. METHODS: Eight patients (50% female) undergoing MR imaging of the skull base for diagnostic purposes (62.5% for vestibular schwannoma surveillance) at a tertiary care center were enrolled to evaluate the safety and efficacy of UTE imaging. CT scans were completed in 37.5% of the patients as part of their workup and used for comparison purposes. The repetition time, short echo time, and long echo time for the UTE sequence were 11, 0.032, and 2.2 msec, respectively. RESULTS: The protocol added 6 min to the total scanning time, and all patients tolerated the sequence without issue. The ossicles, mastoid air cells, antrum, and epitympanum were able to be seen and had a high Dice similarity coefficient when compared to CT (>0.5). UTE allowed for clear delineation of all segments of the facial nerve with a signal-to-noise ratio of 35 (although the BRAVO sequences had a superior ratio of 140). Vestibular schwannomas were able to be distinguished from normal brain parenchyma. CONCLUSIONS: UTE is safe and effective for visualizing anatomic structures not normally seen on traditional MRI, potentially allowing for improved surgical planning in patients. LEVEL OF EVIDENCE: III Laryngoscope, 2024.

Extra-Arachnoidal Dissection and Limited Meatal Drilling for Excision of Giant Vestibular Schwannomas: Improved Facial Nerve Preservation.

Background: Surgical excision of giant (>4 cm size) vestibular schwannomas (VS) with preservation of facial nerve (FN) function remains a challenge. Objective: Our surgical technique using an extra-arachnoid plane of dissection and limited meatal drilling is described with the goal of improving FN preservation. Methods: Surgical results with respect to FN preservation were analyzed for two groups of giant VS patients: Group A-operated between 2002 and 2009 using "standard" surgical technique, group B-operated between 2009 and 2016 using extra-arachnoidal dissection and limited meatal drilling. All patients had a minimum follow-up of 1 year. Results: Group A: Of the 115 patients, total excision was possible in 103 (89.5%), near-total in 7 (6%), and subtotal in 5 (4.3%) patients. At a >6-month follow-up, 68 (59.1%) patients had good FN function (House-Brackmann [H&B] grades 1-2), while 21 (18.3%) patients had poor function (H&B grade 3-5). Grade 6 involvement was seen in 26 (22.6%). Five patients had lower cranial nerve impairment necessitating tracheostomy. Group B: Of the 98 patients, total excision was achieved in 70 (71.4%) patients, near-total in 9 (9.2%), and subtotal in 19 (19.4%). Four patients had repeat surgery; 14 underwent gamma-knife radiosurgery. At >6-month follow-up, 78 (79.5%) patients had good FN function (H&B grades 1-2), while 20 (20.4%) had poor function (H&B grade 3-5). Conclusions: With our 'modified' surgical technique of extra-arachnoidal dissection of VS throughout surgery and limited meatal drilling, an improved rate of functional FN preservation was observed.

Current Understanding of Hearing Loss in Sporadic Vestibular Schwannomas: A Systematic Review.

OBJECTIVE: Hearing loss is the most common initial symptom in patients with sporadic vestibular schwannomas (SVS). Hearing preservation is an important goal of both conservative and surgical therapy. However, the mechanism of SVS-associated hearing loss remains unclear. Thus, we performed this systematic review to summarize the current understanding of hearing loss in the SVS and distill a testable hypothesis to further illuminate its underlying mechanism. METHODS: A systematic review querying four databases (PubMed, Medline, Embase, and Web of Science) was performed to identify studies evaluating hearing loss in patients with SVS and exploring the potential mechanisms of hearing impairment. RESULTS: A total of 50 articles were eligible and included in this review. After analysis, the retrieved studies could be categorized into four types: (1) 29 studies explore the relationship between hearing loss and the growth pattern of the tumor (e.g., tumor size/volume, growth rate, tumor location, etc.); (2) ten studies investigate the potential role of cochlear dysfunction in hearing deterioration, including structural abnormality, protein elevation in perilymph, and cochlear malfunctioning; (3) two studies looked into SVS-induced impairment of auditory pathway and cortex; (4) in the rest nine studies, researchers explored the molecular mechanism underlying hearing loss in SVS, which involves molecular and genetic alterations, inflammatory response, growth factors, and other tumor-associated secretions. CONCLUSIONS: Multiple factors may contribute to the hearing impairment in SVS, including the growth pattern of tumor, cochlear dysfunction, impairment of auditory pathway and cortex, genetic and molecular changes. However, our current understanding is still limited, and future studies are needed to explore this multifactorial hypothesis and dig deeper into its underlying mechanism.

Efficacy and comorbidities of hypofractionated and single-dose radiosurgery for vestibular schwannomas: a systematic review and meta-analysis.

BACKGROUND: Vestibular schwannomas (VS) are tumors of the cerebellopontine angle with significant morbidity, causing hearing loss, tinnitus, and trigeminal and facial nerve compromise. An effective alternative to microsurgical resection is stereotactic radiosurgery (SRS), which can be delivered in either single-fraction (SRS) or hypofractionated stereotactic radiotherapy (hSRT) (3-5 treatments) regimens. It remains unclear which fractionation regimen provides superior outcomes. METHODS: Ovid MEDLINE, EMBASE, CINAHL, and Cochrane Reviews were searched for studies either comparing hSRT with SRS or focusing on hSRT alone in treating VS. Primary endpoints included tumor control, serviceable hearing, tinnitus, and cranial nerve V and VII symptoms. A random-effects analysis was employed to compare pre- and post-treatment effects (hSRT alone) or SRS and hSRT outcomes (two-arm studies). RESULTS: This analysis included 21 studies focusing on hSRT alone and 13 studies comparing SRS and hSRT. Significant heterogeneity was observed. Overall, when hSRT was analyzed alone, crude tumor control was achieved in 94% (95% CI: 88%, 99%) of 1571 patients. There was no difference between pre- and post-treatment odds ratios (OR) of tinnitus, facial, or trigeminal impairment. Serviceable hearing was diminished following hSRT (OR = 0.60, 95% CI: 0.44, 0.83). Comparison with SRS showed no difference with respect to tumor control, serviceable hearing, trigeminal or facial nerve impairment. CONCLUSIONS: hSRT achieved excellent tumor control and, with the exception of serviceable hearing, did not result in worse post-treatment cranial nerve symptomatology. Analysis of comparative studies between hSRT and SRS did not reveal any significant difference in either tumor control or treatment morbidities.

What factors influence treatment decision making in acoustic neuroma? Our experience on 103 cases.

Acoustic Neuromas (AN) are benign tumors of the vestibulocochlear nerve with symptomatology that includes unilateral sensorineural hearing loss, tinnitus, dizziness, facial and/or trigeminal neuropathy. There are different treatment options of AN: watchful waiting, microsurgical resection, stereotactic radiation and the choice depends by many variables such age, health and hearing of patients as size, location and growing status of tumor. The objective of this retrospective study is to better understand the differences in demographic, hearing status, symptoms, tumor characteristics in patients affected by AN presenting at our clinic and analyze the factors that influence the therapeutic choice. One-hundred three patients affected by AN were included in the study. All subjects underwent a detailed clinical interview and audio-vestibular examination, and Magnetic Resonance Imaging (MRI). Tumor status, growing or stable was estimated comparing new size to any previous MRI with at least a 6-month interval. Descriptive statistics were used for clinical and demographic features of patients. Therapeutic choices related to subjective symptoms were assessed with the chi-square test. Treatment options in our sample included watchful waiting, surgical resection and stereotactic radiosurgery. Overall, 17 patients (16.5%) pursued surgical resection via the retrosigmoid approach, 3 patients (2.9%) were treated with gamma knife stereotactic radiosurgery and 83 patients (80.6%) underwent watchful waiting. The decision-making process for AN treatment was based on size of tumor, age, and hearing loss; a statistically significant difference was found at Z test about size of tumor and PTA of patients that underwent retrosigmoid surgery. No statistically significant difference was found at chi-square test between the type of treatment and symptoms (p=0.719). The analysis of the data showed that the main elements taken into consideration for surgery were the size of tumor (p<0.000004) and, secondly, the PTA threshold; the latter may be due to the fact that patients with bigger tumors had greater hearing impairment (p<0.001). Disease progression influenced the therapeutic decision making with a positive correlation between tumor progression and surgery (p<0.001). In our sample, active surveillance was the most adopted option for small tumor, slow growth and old age. Microsurgical resection was the preferred treatment in patients with large tumors, hearing deterioration and rapid growth. Stereotactic radiation has been proposed in a few cases of elderly patients with slow growing tumor and mild hearing loss.

Surgical Treatment of Secondary Trigeminal Neuralgia Induced by Cerebellopontine Angle Tumors: A Single-Center Experience.

OBJECTIVE: Secondary trigeminal neuralgia (TN) caused by cerebellopontine angle (CPA) tumors are rare, although TN may be a primary manifestation in the neurosurgery department. In this study, we aimed to retrospectively assess patients with CPA tumor-induced TN from a single center. METHODS: Of 819 consecutive patients with TN treated at our center between 2007 and 2017, 36 with CPA tumor-induced TN were enrolled, and their medical and surgical records were analyzed. RESULTS: The 36 patients accounted for 4.4% of all patients with TN. A comparison of patients with classic and tumor-induced TN indicated significant intergroup differences in the mean age at surgery (58.94 vs. 49.33 years, P = 0.000), the mean age at onset of TN (52.01 vs. 38.04 years), and affected side (298/485 vs. 22/14 in left/right, P = 0.006); no such difference was noted in the sex ratio (0.598 vs. 0.385, P = 0.214). The rates of excellent, good, and fair clinical outcomes were 80.56%, 13.89%, and 2.78%, respectively. The offending vessels found during surgery included the superior and anterior inferior cerebellar arteries in 3 and 4 cases, respectively. Postoperative complications included aseptic meningitis (1 case), facial numbness (2 cases), hearing disturbance (3 cases), facial palsy (4 cases), hemorrhage (1 case), and diplopia (2 cases). CONCLUSIONS: Secondary TN caused by CPA tumors is not as frequent as classic TN. Compared with classic TN, tumor-induced TN is characterized by symptom onset and surgery at a younger age. Direct compression rather than chemical irritation is the cause of secondary TN.

Vestibular Schwannoma Resection in a Consecutive Series of 502 Cases via the Retrosigmoid Approach: Technical Aspects, Complications, and Functional Outcome.

OBJECTIVE: Outcome in vestibular schwannoma (VS) surgery has improved enormously over the last decades. Surgical positioning remains a matter of discussion. A standardized protocol for diagnostics and management has been applied and evaluated for complications and functional outcome. METHODS: We examined 502 VS tumors in 483 patients (227 men and 256 women) between 2005 and 2016. According to our patient selection and treatment algorithm, 488 operations (97%) were performed in the semi-sitting position, and 14 (3%) were in the supine position. Auditory and facial functions were analyzed before and after surgery as were perioperative complications. RESULTS: There were 182 patients (36%) with small tumors (Hannover classification T1-T3A) and 320 (64%) large tumors (T3B or T4). Of the patients, 14% were neurofibromatosis type 2 cases. Complete tumor resection was achieved in 96.4%. Hearing preservation occurred in 44% of patients with small tumors and 23% of those with large tumors (Hannover classification), and correlated significantly with tumor size (P < 0.001). Facial palsy (House Brackmann grades II-VI) was present in 63 patients before and in 185 patients after surgery. Useful facial function (House Brackmann grades I-III) early after surgery was maintained in 86% of patients with small tumors and in 77% of patients with large tumors. Intraoperative complications included air embolism in 45 cases (9%), sinus injury in 3 cases, cerebrospinal fluid leakage in 46 cases (9%), and local hemorrhage in 19 cases (4%). Surgical revision was indicated in 31 cases (6%). CONCLUSIONS: In a standardized setting, the semi-sitting position allowed a safe approach. This setting offers the advantage of bimanual tumor nerve handling by the surgeon and an optimal visualization of important functional structures.

Painful Trigeminal Neuropathy Attributed to a Space-occupying Lesion Presenting as a Toothache: A Report of 4 Cases.

Painful trigeminal neuropathy attributed to a space-occupying lesion (code 13.1.2.5 in the International Classification of Headache Disorders, 3rd edition [beta version]) is an orofacial pain condition that has characteristics of classical trigeminal neuralgia but is caused by a space-occupying lesion. We present 4 cases of intracranial lesions mimicking odontogenic pain as follows: case 1, a 61-year-old woman presented with a chief complaint of aching soreness in the right mandibular molar area for 1 year; case 2, a 59-year-old man presented with severe pain in the left maxillary and mandibular molars; case 3, a 72-year-old man presented with a chief complaint of facial shock-like pain on the left side; and case 4, a 75-year-old man presented with a chief complaint of paroxysmal pain and numbness in the buccal gingiva of the right mandibular molar region. Cases 1 and 2 had trigeminal neuralgia, which had previously been incorrectly attributed to osteoma and maxillary sinus retention cyst, respectively, and resulted in inappropriate dental surgical procedures. All patients subsequently underwent magnetic resonance imaging, and the results were consistent with intracranial disease. Magnetic resonance images revealed acoustic neuromas in the cerebellopontine angle in cases 1, 2, and 4 and a small meningioma near the entry to the left Meckel cave in case 3. Cases 1, 3, and 4 had these lesions removed; after which, their pain resolved. Before dental treatment, dental practitioners should focus not only on dental imaging but also on the patient's medical history and pain characteristics.

How to Address Small- and Medium-Sized Acoustic Neuromas with Hearing: A Systematic Review and Decision Analysis.

OBJECTIVE: Small- and medium-sized acoustic neuromas (ANs) increase in both number and proportion. Observation, radiosurgery, and microsurgery are all used to treat this disease; however, the appropriate treatment is controversial, especially in patients with hearing. METHODS: We searched the MEDLINE, EMBASE, CENTRAL (Cochrane Central Register of Con-trolled Trials), LILACS (Latin American and Caribbean Center on Health Sciences Information), and CMB (Chinese Biomedical Database) databases without limits on the language and the time of publication. For the wait-and-scan strategy, we included the population-based prospective studies with sufficient follow-up time and information. We also attempted to locate high-level evidence that compared radiosurgery with microsurgery. The data were extracted from the studies to synthesize the probabilities. We surveyed 60 patients with small- and medium-sized ANs to plot the outcomes on a linear scale to measure the utility. RESULTS: Eight studies met the inclusion criteria of the wait-and-scan strategy, and 3 grade II evidence studies were found that compared microsurgery with radiosurgery. After synthesizing the data in 3 groups, the preservation of useful hearing was 58.9%, 60.2%, and 4.3%, whereas the rate of tumor control was 71.1%, 97.0%, and 94.3%, respectively. The expected value for radiosurgery was 0.68, whereas the expected values for wait-and-scan and surgery were 0.64 and 0.28, respectively. CONCLUSION: On the basis of the evidence, radiosurgery is the optimal choice for small- and medium-sized ANs. Because of the current difficulty with understanding the natural history of ANs, we suggest that there is a need for new evidence and a health economics assessment to update this result.

Radiosurgery for vestibular schwannomas.

This article investigates the role of radiosurgery and stereotactic radiotherapy in the management of vestibular schwannomas (VS), reviewing the authors' own prospective cohort and the current literature. For patients with large Stage IV VS (according to the Koos classification), a combined approach with deliberate partial microsurgical removal followed by radiosurgery to the residual tumor is proposed. The authors' cohort is unique with respect to the size of the population and the length of the follow-up, and demonstrates the efficacy and safety of VS radiosurgery, with particular regard to its high rate of hearing preservation.

Calculating the tumor volume of acoustic neuromas: comparison of ABC/2 formula with planimetry method.

OBJECTIVE: The ABC/2 equation is commonly applied to measure the volume of intracranial hematoma. However, the precision of ABC/2 equation in estimating the tumor volume of acoustic neuromas is less addressed. The study is to evaluate the accuracy of the ABC/2 formula by comparing with planimetry method for estimating the tumor volumes. METHODS: Thirty-two patients diagnosed with acoustic neuroma received contrast-enhanced magnetic resonance imaging of brain were recruited. The volume was calculated by the ABC/2 equation and planimetry method (defined as exact volume) at the same time. The 32 patients were divided into three groups by tumor volume to avoid volume-dependent overestimation (<3 ml, 3-6 ml and >6 ml). RESULTS: The tumor volume by ABC/2 method was highly correlated to that calculated by planimetry method using linear regression analysis (R2=0.985). Pearson correlation coefficient (r=0.993, p<0.001) demonstrates nearly perfect association between two methods. CONCLUSIONS: The ABC/2 formula is an easy method in estimating the tumor volume of acoustic neuromas that is not inferior to planimetry method.

Evaluation of variation in the course of the facial nerve, nerve adhesion to tumors, and postoperative facial palsy in acoustic neuroma.

Objective To investigate the variation in the course of the facial nerve (FN) in patients undergoing acoustic neuroma (AN) surgery, its adhesion to tumors, and the relationship between such adhesions and postoperative facial palsy. Methods The subjects were 356 patients who underwent AN surgery in whom the course of the FN could be confirmed. Patients were classified into six groups: ventro-central surface of the tumor (VCe), ventro-rostral (VR), ventro-caudal (VCa), rostral (R), caudal (C), and dorsal (D). Results The FN course was VCe in 185 cases, VR in 137, VCa in 19, R in 10, C in 4, and D in one. For tumors < 1.5 cm, VCe was most common. For tumors ≥ 1.5 cm, the proportion of VR increased. No significant difference was observed between the course patterns of the FN in terms of postoperative FN function, but for tumors > 3.0 cm, there was an increasing tendency for the FN to adhere strongly to the tumor capsule, and postoperative facial palsy was more severe in patients with stronger adhesions. Conclusions The VCe pattern was most common for small tumors. Strong or less strong adhesion to the tumor capsule was most strongly associated with postoperative FN palsy.

Cirurgia da base do crânio: uma desafiadora especialidade da medicina moderna / Skull base surgery: a challenging speciality of modern medicine

A cirurgia da base do crânio emerge como uma especialidade da medicina moderna. Seu principal objetivo é tratar lesões, principalmente tumores, situados em complexa topografia anatômica e que, há duas décadas, eram considerados inoperáveis. O objetivo desta revisão é fornecer ao médicos generalistas uma visão dos aspectos conceituais, históricos, patológicos, epidemiológicos, clínicos e terapêuticos em cirurgia da base do crânio.

Skull base surgery has emerged as a specialty in modern medicine. Its main objective is to treat injuries, especially tumors located in anatomically complex sites that two decades ago were considered inoperable. The aim of this review is to provide general practitioners with a view of conceptual, historical, pathological, epidemiological, clinical and therapeutic aspects of skull base surgery.

The keyhole retrosigmoid approach to the cerebello-pontine angle: indications, technical modifications, and results.

OBJECTIVES: Establish the versatility and usefulness of the keyhole retrosigmoid approach to the cerebello-pontine angle (CPA) in various pathologies. DESIGN: Prospective clinical study. SETTING: Tertiary referral university hospital. METHODS: One hundred twenty-one patients with various pathologies of the CPA underwent the relevant investigations and were operated upon by the retrosigmoid microendoscopic approach. The technical modifications and progression of our technique are described. RESULTS: This group consisted of 121 patients (103 men and 28 women). The pathologies included were 60 acoustic neuromas, 28 vestibular neurectomies, nine meningiomas, and four arachnoid cysts. For nonmass lesions, no additional facial nerve injury or deterioration of hearing occurred. Total excision of mass lesions was achieved in 94.5% of cases. Facial nerve integrity was preserved in 92.3% of cases with mass lesions and permanent facial paralysis occurred in 8.3%. There were no mortalities, and the most frequent complication was a delayed cerebrospinal fluid leak from the site of the wound (15%), which was managed conservatively in all cases. CONCLUSIONS: The keyhole retrosigmoid approach is a versatile one. It can be used to deal with different pathologies through a unified access, and with the increasing exclusive use of endoscopes, a truly minimally invasive surgery can be achieved.

Schwannoma vestibular: involução tumoral espontânea / Vestibular Schwannoma: spontaneous tumor involution

A história natural dos schwannomas vestibulares ainda não está totalmente elucidada, mas sua maioria tende a apresentar crescimento lento, muitos permanecendo sem sintomas durante toda a vida do paciente. Cerca de 69 por cento deste tipo de tumor diagnosticados não apresentam crescimento e, destes, 16 por cento chegam a apresentar regressão tumoral. Considerando os tumores que apresentam crescimento, cerca de 70 por cento crescem menos de 2 mm ao ano. O avanço nos métodos de diagnóstico por imagem, particularmente à ressonância magnética com contraste de gadolínio, permite o diagnóstico cada vez mais de lesões com sintomas mínimos e tamanhos menores. O tratamento de escolha para estes tumores ainda é a ressecção completa do tumor. As técnicas cirúrgicas apresentaram grande avanço nas últimas décadas, o que possibilitou diminuição da mortalidade. Assim, a cirurgia, que antes tinha como objetivo apenas a ressecção completa do tumor, agora visa também à preservação da audição e da função do nervo facial. Considerações finais: Considerando-se sua história natural, abre-se a possibilidade de uma conduta conservadora já que o ritmo de crescimento no primeiro ano após o diagnóstico prediz o comportamento do tumor nos próximos anos. A conduta conservadora não implica em repúdio à cirurgia, devendo ser utilizada em casos de aumento tumoral, piora dos sintomas ou desejo do paciente. Além disso, em relatos de literatura não há diferença estatisticamente significante entre os pacientes submetidos à cirurgia logo após o diagnóstico ou após conduta conservadora inicial, no que diz respeito às seqüelas pós-operatórias.

The natural history of Vestibular Schwannomas (VS) is yet not totally known, but most of them have the tendency to slow growth, sometimes without any kind of symptoms during the individual’s entire time. About 69 percent of diagnosed VS do not grow at all and 16 percent of these can even regress. Considering tumors that grow, about 70 percent have grown less than 2mm an year. Advanced radiological diagnosis, especially magnetic resonance imaging with gadolinium helps us diagnose small and less symptomatic tumors. Treatment of choice still is complete tumor resection. Surgical approaches have improved considerably and have helped preserve facial nerve function and hearing. Considering VS’s natural history, there is a possibility for conservative treatment for these tumors, because their growth in the first year after diagnosis predicts tumor growth behavior in the next years. Surgery should be done in cases of tumor growth, patient’s desire or symptoms worsening. Moreover, in terms of postoperative sequelae, there is no difference between patients who underwent surgery immediately after diagnosis and those who underwent initial conservative treatment for these tumors.

Cystic acoustic neuromas.

Predominantly cystic acoustic neuromas are rare and they usually present with clinical and radiological features different from their more common solid counterparts. Two cases of cystic acoustic neuromas are reported here.