Cranial Base Surgery

Fourth ventricle tumor surgery complications

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Fourth ventricle tumor surgery complications

Fourth ventricle tumor surgery is delicate and carries specific risks due to the complex anatomy of the region. The fourth ventricle lies in the posterior fossa of the brain, nestled between the brainstem and cerebellum. Because of this, complications can involve vital neurological structures.

🔴 Neurological Complications

Cranial Nerve Deficits

Especially CN VI (abducens), CN VII (facial), and CN VIII (vestibulocochlear).

May cause diplopia, facial weakness, or hearing loss.

Cerebellar Dysfunction

Ataxia, dysmetria, intention tremor.

Can be transient or permanent.

Brainstem Injury

Risk of respiratory or cardiovascular instability.

It can lead to coma or death in extreme cases.

Mutism / Cerebellar Cognitive Affective Syndrome

Especially in pediatric patients after resection of medulloblastomas or ependymomas.

Characterized by mutism, emotional lability, and executive dysfunction.

💧 CSF-related Complications

Hydrocephalus (pre- or post-operative)

Due to obstruction of CSF pathways (aqueduct or outlets of the fourth ventricle).

May require an external ventricular drain (EVD) or VP shunt.

CSF Leak / Pseudomeningocele

From poor dural closure or pressure buildup.

Risk of infection or wound healing issues.

Meningitis / Ventriculitis

Especially if there’s a CSF leak or prolonged drain use.

💉 Vascular Complications

Hemorrhage

Intraoperative bleeding from a tumor or surrounding vessels.

Postoperative hematoma causing brainstem compression.

Ischemia

Injury to perforating arteries (e.g., branches of the posterior inferior cerebellar artery – PICA).

It can cause infarcts in the brainstem or cerebellum.

🛌 Systemic and General Complications

Infection

Seizures (rare for the posterior fossa)

Respiratory compromise (especially in children or after brainstem manipulation)

Wound complications

🧠 Tumor-specific factors

Ependymomas: Adherence to the floor of the 4th ventricle increases brainstem injury risk.

Medulloblastomas: prone to CSF spread, so thorough surgical and oncologic planning is key.

Choroid plexus tumors: highly vascular, bleeding risk.

Cohort studies

In a large multicenter cohort study Persson et al. investigate postoperative word-finding abilities in children undergoing posterior fossa tumor surgery (PFTs), with data from 184 children across Europe. The authors address a critical yet understudied postoperative complication—word-finding difficulty, which goes beyond classic cerebellar mutism syndrome (CMS) and focuses on more subtle higher-order language impairments 1)

The study’s key strength lies in its pre- and postoperative comparisons using a speeded picture-naming test, providing quantitative insights into word retrieval speeds. Interestingly, the results reveal no significant change between pre- and postoperative performance on average. This means that while some children improved, others declined, underscoring the heterogeneous outcomes in PFT surgeries.

A striking finding is that 95% of children performed more than two standard deviations slower than age norms after surgery, despite no aggregate decline. This discrepancy suggests that even without a gross drop in individual scores, the cohort as a whole demonstrates clinically significant delays, potentially overlooked in standard assessments.

The study identifies fourth ventricle tumor as a specific risk factor (B = -4.09, p < 0.05), linking it to possible damage of the dentato-thalamo-cortical pathway. This aligns with previous neuroanatomical models implicating cerebellar-thalamo-cortical circuits in language function, not just motor planning.

From a clinical perspective, these findings call for routine postoperative language screening—even in patients who do not develop mutism—to detect subtle deficits that may affect communication and academic performance. Furthermore, early intervention strategies may be needed, particularly for children with tumours in higher-risk locations.

This study contributes valuable evidence supporting the existence of subtle yet functionally important postoperative language impairments in children with PFTs. It urges the neurooncology and neuropsychology communities to broaden the scope of postoperative assessments to include not only mutism but also word-finding and higher cognitive-linguistic functions.

1)

Persson K, Grønbæk J, Tiberg I, Fyrberg Å, Castor C, Andreozzi B, Frič R, Hauser P, Kiudeliene R, Mallucci C, Mathiasen R, Nyman P, Pizer B, Sehested A, Boeg Thomsen D; CMS study group. Postoperative word-finding difficulties in children with posterior fossa tumours: a crosslinguistic European cohort study. Childs Nerv Syst. 2025 Mar 12;41(1):128. doi: 10.1007/s00381-025-06787-4. PMID: 40075014; PMCID: PMC11903548.

Mayo Clinic Vestibular Schwannoma Quality of Life Index 

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“Improving access to vestibular schwannoma quality of life research through multilanguage translations of the Mayo Clinic Vestibular Schwannoma Quality of Life Index” (*Carlson et al., J Neurosurg. 2025;142(Suppl):S2. doi:10.3171/2024.11.JNS242317*)

This article reports on the translation of the Mayo Clinic Vestibular Schwannoma Quality of Life Index into six widely spoken languages: Simplified Chinese, Spanish, Japanese, Arabic, French, and Norwegian. It is presented as a digital supplement to the *Journal of Neurosurgery* and is positioned as a response to a key limitation in vestibular schwannoma research: the lack of validated, multilingual tools to assess the quality of life (QOL) in a culturally diverse patient population.

The VSQOL Index, developed originally in English, is a domain-specific tool covering eight core categories that reflect the multidimensional burden of VS, ranging from hearing loss to psychosocial and cognitive impacts. The article emphasizes accessibility, global equity in research, and the potential for cross-cultural validation.

2. Strengths

– Timely and Inclusive Effort: In a field increasingly aware of the importance of patient-reported outcomes (PROs), the expansion of the VSQOL Index to multiple languages addresses a real and urgent need. The effort reflects a commitment to diversity, equity, and inclusion (DEI) in neurosurgical research.

– Breadth of Domains: The eight domains covered are comprehensive and clinically relevant, reflecting an understanding of VS as a condition that affects patients beyond physical symptoms.

– Noncommercial Open Access: Making the tool freely available for noncommercial use significantly boosts its adoption potential in both research and clinical settings.

– Forward-Looking Implementation Strategy: By inviting further translations and offering a methodology for doing so, the authors promote scalability and community collaboration.

3. Limitations and Areas for Improvement

– Lack of Validation Data for Translations: A critical omission is the absence of psychometric validation data for the translated versions. Translation alone does not ensure cultural equivalence or measurement validity. Were back-translations performed? Were cognitive interviews or pilot tests conducted in native-speaking populations?

– No Discussion on Linguistic/Cultural Adaptation Challenges: Certain concepts (e.g., “regret” or “impact on employment”) may not translate directly or may have different cultural connotations, particularly in non-Western contexts. This nuance is missing.

– Digital Supplement Format: The article feels more like a resource announcement than a full scientific paper. There’s no detailed methodology on how the translations were produced, reviewed, or tested. A table comparing the original and translated items or discussing challenges in specific languages would have enriched the value.

– Unclear How This Affects Clinical Decision-Making: Although QOL is important, the article could have outlined practical examples of how this tool has been or could be used to guide treatment planning, shared decision-making, or monitoring outcomes in real-world clinics.

4. Future Directions

– Cross-Cultural Validation Studies: Essential next steps include conducting validation study in diverse populations to confirm that the VSQOL Index is both reliable and sensitive across languages and cultures.

– Integration into Registries and Trials: The authors could propose integrating the VSQOL Index into prospective multicenter studies or national registries, which would increase the visibility and utility of the tool.

– Digital Implementation: The use of a mobile app or integration with electronic health records (EHRs) for real-time patient input could enhance its impact and usability in clinical workflows.

Conclusion

Carlson et al. make a significant and commendable contribution to the field of vestibular schwannoma research by expanding the reach of a multidimensional QOL assessment tool through multilingual translation. However, to truly fulfill its potential, the translated versions must undergo rigorous psychometric validation, and future work should aim to embed the Index in clinical and research settings more explicitly. As it stands, this is a valuable first step—but just the beginning—in making QOL data accessible and actionable in a globalized neurosurgical landscape.

Arginine Vasopressin Deficiency Diagnosis

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🧪 Arginine Vasopressin Deficiency Diagnosis

(*formerly known as Central Diabetes Insipidus*)

🧠 Background

Deficiency results in:

Common causes:

🔍 Initial Assessment

Test Finding in AVP Deficiency
Serum sodium Often elevated
Plasma osmolality >295 mOsm/kg
Urine osmolality <300 mOsm/kg
Urine specific gravity <1.005 g/mL

💧 Water Deprivation Test (optional if diagnosis unclear)

see Water Deprivation Test

– Progressive fluid restriction – Measure: body weight, plasma osmolality, urine osmolality – Administer desmopressin (DDAVP) when appropriate

Finding AVP-D (Central) Nephrogenic DI Primary Polydipsia
Baseline urine osm Low Low Low-normal
Response to DDAVP ↑ >50% No change Slight ↑

🧠 Imaging

* Pituitary MRI to rule out structural causes * Look for loss of posterior pituitary bright spot

🏥 Postoperative Bedside Screening

Red flags (first 72h post-surgery):

  • Urine output >250 mL/h for 2–3 h
  • Urine SG <1.005 g/mL
  • Rising serum sodium >145 mmol/L

Patient self-monitoring strategy:

  • Use urine dipsticks (e.g., Combur-10)
  • Cut-off ≥1.015 g/mL reliably excludes hypotonic urine

→ Reduces need for nurse-led testing by ~50% 1).

It advances the concept of patient-participatory diagnostics and offers a replicable approach to screen for AVP-D. With thoughtful implementation, it has the potential to optimize workflows and empower patients, though accuracy limitations and clinical oversight remain essential.

👤 Patient Self-Monitoring Strategy for AVP Deficiency

Self-monitoring of urine specific gravity (SG) offers a non-invasive, accessible method for early identification of Arginine vasopressin deficiency (AVP-D) — particularly useful in the early postoperative period after pituitary surgery.

🎯 Objective

To enable patients to detect hypotonic urine (SG < 1.005 g/mL), a hallmark of AVP-D, using simple tools and clear thresholds, reducing reliance on continuous nurse monitoring.

🧪 Tools Required

Tool Description
Urine dipsticks e.g., Combur-10 test strips
SG reference chart Provided to patient (color guide or numeric)
Fluid intake/output diary Optional but useful
Basic education Brief verbal or written instructions

📌 Step-by-Step Monitoring Protocol

1. Frequency: Every 2–4 hours during the first 72h post-op (or as indicated) 2. Record:

  1. Urine SG using dipstick
  2. Time of measurement
  3. Urine volume (if known)

3. Interpretation:

  1. If SG < 1.005 → Alert nurse or clinician
  2. If SG ≥ 1.015 → No action needed

4. Look for associated symptoms:

  1. Excessive thirst (polydipsia)
  2. Frequent urination (polyuria)
  3. Light-colored or clear urine
  4. Dizziness or fatigue

A threshold of 1.015 g/mL is considered safe to rule out hypotonic urine and avoid missing AVP-D, based on current evidence.

✅ Advantages

  • Reduces nurse-led SG testing by ~50% 2)
  • Promotes early detection of AVP-D
  • Encourages patient engagement and education
  • Minimizes unnecessary interventions

⚠️ Considerations

  • Patients must be briefly trained on dipstick use and interpretation
  • Not suitable for:
    1. Patients with cognitive impairment
    2. Pediatric patients (without caregiver)
    3. Severe visual deficits
  • Always confirm low SG findings with clinical review and serum sodium

Combine self-monitoring of SG with daily weight and serum sodium trends for robust early detection of AVP-D in neurosurgical patients.

✅ Summary Table

Step Goal
Clinical evaluation Identify symptoms: polyuria, polydipsia
Serum/urine osmolality Confirm dilute urine & hyperosmolar plasma
Water deprivation test Differentiate AVP-D from other causes
Pituitary MRI Identify structural abnormalities
Urine SG monitoring post-op Early detection & workload reduction

When feasible, train patients to monitor urine SG using dipsticks. Use a safety threshold (SG ≥ 1.015) to minimize false negatives.

🔬 Imaging & Laboratory Markers of Diabetes Insipidus (DI)

🧠 T1-weighted MRI: Hyperintensity and ADH

Antidiuretic hormone (ADH) appears as a hyperintensity (HI) on T1-weighted magnetic resonance imaging in:

Key findings:

  • Disappearance of HI in the posterior lobe is a marker of ADH deficiency, often observed in DI.
  • Appearance of HI in the stalk suggests disturbances in ADH transport.

3)

💉 Serum Sodium: Perioperative Laboratory Markers

* An increase in serum sodium ≥2.5 mmol/L is a positive marker of postoperative diabetes insipidus with:

  • 80% specificity

* A serum sodium ≥145 mmol/L postoperatively indicates DI with:

  • 98% specificity

These thresholds help identify patients at risk and guide early treatment decisions after endoscopic transsphenoidal surgery (ETSS).

4)

Early changes in T1 hyperintensity and postoperative serum sodium can serve as non-invasive predictors of DI and support clinical decision-making.

References

1)

Nollen JM, Brunsveld-Reinders AH, Biermasz NR, Verstegen MJT, Leijtens E, Peul WC, Steyerberg EW, van Furth WR. Patient Participation in Urine Specific Gravity Screening for Arginine Vasopressin Deficiency in an Inpatient Neurosurgical Clinic. Clin Endocrinol (Oxf). 2025 Mar 27. doi: 10.1111/cen.15241. Epub ahead of print. PMID: 40145244.
2)

Nollen JM et al., *Clin Endocrinol (Oxf)*, 2025
3)

Hayashi Y, Kita D, Watanabe T, Fukui I, Sasagawa Y, Oishi M, Tachibana O, Ueda F, Nakada M. Prediction of postoperative diabetes insipidus using morphological hyperintensity patterns in the pituitary stalk on magnetic resonance imaging after transsphenoidal surgery for sellar tumors. *Pituitary*. 2016 Dec;19(6):552-559. PMID: 27586498
4)

Schreckinger M, Walker B, Knepper J, Hornyak M, Hong D, Kim JM, Folbe A, Guthikonda M, Mittal S, Szerlip NJ. Post-operative diabetes insipidus after endoscopic transsphenoidal surgery. *Pituitary*. 2013 Dec;16(4):445-51. PMID: 23242859

Associations of Microvascular Risk Factors with Sporadic Vestibular Schwannoma Outcomes Following Stereotactic Radiosurgery

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The article in *Otolaryngology–Head and Neck Surgery* provides a valuable investigation into how microvascular risk factors might influence outcomes following vestibular schwannoma radiosurgery. By assessing a large cohort of 749 patients treated between 2000 and 2022, the study explores the connections between microvascular risk factors—like hypertension, smoking, obesity, and coronary bypass history—and the efficacy and side effects of SRS 1)

Strengths

1. Large Sample Size and Cohort Design: The authors reviewed a substantial cohort of 749 patients across two decades. This sample size enhances the reliability and generalizability of findings, especially when considering the rare nature of VS.

2. Specific Risk Factors Analysis: The study dives into specific microvascular risk factors, evaluating how each may impact tumor control and adverse outcomes such as facial nerve paresis and hearing loss. This approach allows for a nuanced understanding of the multifactorial risks associated with SRS in VS treatment.

3. Clinical Relevance for Patient Counseling: The findings offer practical implications for clinical counseling. For example, identifying smoking as a risk factor for accelerated hearing loss and hypertension as a predictor for facial nerve weakness can help clinicians guide patients more effectively regarding the potential risks of SRS based on individual health backgrounds.

4. Statistical Approach: The use of Cox proportional hazards regression to assess associations and the adjustment for variables like age and ipsilateral hearing status in hearing loss analysis provide a robust statistical foundation, increasing the validity of the results.

Limitations

1. Lack of Mechanistic Insight: While the study identifies correlations between microvascular risk factors and SRS outcomes, it does not provide insights into the biological mechanisms. The authors hypothesize that microvascular hyalinization and ischemia could play a role in VS tumor control, yet no direct evidence is presented.

2. Limited Data on Tumor Control: Despite a detailed investigation of complications, the study lacks significant findings regarding tumor control in relation to microvascular risk factors. This could be due to limited follow-up on tumor growth or insufficient sensitivity of the study to detect such associations, limiting the applicability of the findings to tumor management.

3. Potential Confounding Factors: Although the study adjusts for age and ipsilateral hearing status, other potential confounding factors such as overall health status, treatment modalities prior to SRS, and specific lifestyle factors were not discussed in detail, which might influence outcomes like hearing loss or facial nerve complications.

4. Limited Generalizability Beyond the Study Setting: Conducted within a single tertiary academic center, results might not fully represent diverse patient populations, especially those managed in non-academic or smaller medical centers where treatment protocols may differ.

Conclusion

This study makes a notable contribution to understanding how microvascular risk factors may affect specific outcomes following SRS for sporadic VS. The association of hypertension and coronary artery bypass surgery history with facial nerve paresis, as well as smoking history with accelerated hearing loss, provides valuable insights for clinical decision-making and patient counseling. However, limitations in mechanistic insight and generalizability, as well as the lack of significant findings on tumor control, suggest the need for further research. Future studies could benefit from exploring the biological mechanisms at play and expanding data collection across multiple centers for broader applicability.

1)

Dornhoffer JR, Babajanian EE, Khandalavala KR, Marinelli JP, Daher GS, Lohse CM, Link MJ, Carlson ML. Associations of Microvascular Risk Factors with Sporadic Vestibular Schwannoma Outcomes Following Stereotactic Radiosurgery. Otolaryngol Head Neck Surg. 2024 Nov 7. doi: 10.1002/ohn.1038. Epub ahead of print. PMID: 39506614.

Vestibular Schwannoma Koos Grade 1

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Vestibular Schwannoma Koos Grade 1

Vestibular Schwannoma Koos grading scale 1 involves only the internal auditory canal without extension into the cerebellopontine angle (CPA).

– These tumors are typically less than 1 cm in diameter.

Clinical features

– They often present with early symptoms such as unilateral hearing loss, tinnitus (ringing in the ears), or a sensation of fullness in the ear.

Treatment

Treatment for a Koos Grade 1 vestibular schwannoma is typically aimed at preserving hearing and avoiding damage to surrounding structures.

Common management options include:

1. Observation with regular imaging, particularly if the tumor is asymptomatic or if the patient’s age and general health suggest that intervention is not immediately necessary.

2. Surgical resection to remove the tumor, especially if symptoms are progressive or if the tumor is growing.

3. Stereotactic radiosurgery (such as Gamma Knife), which is often used for tumors that are difficult to access surgically or when hearing preservation is a priority.

For Koos Grade I vestibular schwannomas, there is typically no compression of critical structures, and treatment options often involve active surveillance or SRS rather than surgery. These small tumors may not cause immediate symptoms and can often be monitored with regular imaging to track any growth.

Prognosis

The prognosis for Koos Grade 1 vestibular schwannomas is generally good, particularly when they are treated early. However, given the slow-growing nature of many Koos Grade I schwannomas, the necessity and timing of intervention remain topics of ongoing debate in neurosurgery, with individualized treatment being essential

Prospective observational studies

This study by Levivier et al. 1) presents an argument for early intervention with Gamma Knife Surgery (GKS) in patients with Koos grade I vestibular schwannomas (VS), suggesting it as a superior approach to the “wait and see” strategy. However, a critical examination reveals substantial limitations and questions regarding the validity of these recommendations, particularly concerning the study’s methodology and interpretation of results.

1. Short Follow-Up Period and Limited Long-Term Data: The mean follow-up in this study was a mere 1.3 years, with a range from 0.6 to 3.6 years, which is alarmingly short given the slow-growing nature of vestibular schwannomas. Tumors in this early stage often exhibit minimal or no growth over years, making this follow-up insufficient to draw conclusions about long-term outcomes, especially in terms of tumor control and cranial nerve preservation. With such limited follow-up, any claims regarding the benefits of early GKS are speculative at best.

2. Lack of Comparison with Observation Group: The study fails to include a direct comparison group of patients managed with observation, which is a common approach for small, asymptomatic, or minimally symptomatic Koos I tumors. Without this essential control, the assertion that early GKS is preferable to a “wait and see” strategy lacks robust evidence. This absence is particularly significant, as previous studies have shown that many Koos I VS can be safely observed without immediate intervention.

3. Inconsistent Hearing Preservation Results and Dose Concerns: The reported hearing preservation rate of 85% appears promising; however, the authors overlook the fact that hearing can often be maintained in Koos I tumors without intervention, as tumor growth rates are typically low. Additionally, the study does not adequately discuss the risks of radiation exposure to the cochlea and the potential for hearing deterioration over time, especially given the mean cochlear dose of 4.1 Gy, which could have cumulative adverse effects.

4. Overstatement of Preliminary Data: The authors prematurely advocate for early GKS based on “preliminary data,” which lacks the rigor and maturity required for such a definitive recommendation. Promoting early intervention based on short-term data may expose patients to unnecessary risks, especially considering that many Koos I tumors remain asymptomatic or progress very slowly. The recommendation for early GKS is therefore premature, and further research with a longer follow-up is essential before suggesting that patients with asymptomatic or minimally symptomatic tumors should undergo early intervention.

5. Methodological Concerns in Dosimetric Analysis: The study’s focus on dosimetric factors, while important, appears overly simplistic in suggesting that cochlear dose alone can predict hearing preservation. Hearing outcomes in VS are multifactorial, and the authors’ narrow focus on dose metrics overlooks other critical factors that could influence outcomes, such as baseline hearing quality, individual patient anatomy, and the biological response to radiation.

Conclusion: In summary, this study’s recommendation for early GKS in Koos I vestibular schwannomas is founded on weak preliminary data, a limited follow-up, and an absence of a control group for observation. The authors’ enthusiasm for early intervention is unwarranted without more robust, long-term evidence. Until such data is available, it would be prudent to adhere to a conservative approach of observation for Koos I tumors, reserving intervention for cases where there is documented tumor progression or symptomatic deterioration.

Retrospective cohort studies

The VISAS-K1 study is a multicenter retrospective analysis comparing stereotactic radiosurgery (SRS) with active surveillance in the management of Koos grade I vestibular schwannomas (VS). The study aimed to evaluate the safety and efficacy of SRS versus observation for these small, intracanalicular tumors.

Study Design and Methods:

Participants: The study included 142 patients with Koos grade I VS, divided into two groups: those who underwent SRS and those who were observed without immediate intervention.

Matching: Propensity score matching was utilized to balance demographics, tumor size, and audiometric data between the two groups, aiming to reduce selection bias.

Follow-up: The median follow-up period was 36 months, with some patients monitored up to 8 years.

Key Findings:

Tumor Control:

The SRS group achieved a 100% tumor control rate at both 5 and 8 years. In contrast, the observation group had control rates of 48.6% at 5 years and 29.5% at 8 years, indicating a significant advantage for SRS in preventing tumor progression. Hearing Preservation:

Preservation of serviceable hearing was comparable between the two groups. At 5 years, 70.1% of patients in the SRS group and 53.4% in the observation group maintained serviceable hearing, with no statistically significant difference (P = .33). Neurological Function:

Patients in the SRS group had a reduced likelihood of developing tinnitus (odds ratio [OR] = 0.46, P = .04), vestibular dysfunction (OR = 0.17, P = .002), and overall cranial nerve dysfunction (OR = 0.49, P = .03) at the last follow-up compared to those under observation. Conclusions:

The VISAS-K1 study suggests that SRS offers superior tumor control and a lower risk of cranial nerve dysfunction for patients with Koos grade I vestibular schwannomas, without compromising hearing preservation, compared to active surveillance. These findings support the consideration of SRS as a primary treatment option for this patient population 2).

Critical Considerations:

Study Design Limitations: As a retrospective analysis, the study may be subject to selection biases and unmeasured confounding factors, despite efforts to balance groups through propensity score matching.

Follow-up Duration: The median follow-up of 36 months may not fully capture long-term outcomes, especially given the slow-growing nature of vestibular schwannomas.

Outcome Measures: The assessment of cranial nerve function and hearing preservation relies on clinical evaluations that may vary between centers, potentially affecting the consistency of reported outcomes.

In summary, while the VISAS-K1 study provides valuable insights into the management of small vestibular schwannomas, its retrospective nature and potential biases necessitate cautious interpretation of the results. Prospective, randomized controlled trials with standardized outcome assessments are needed to confirm these findings and guide clinical decision-making.

1)

M. Levivier, C. Tuleasca, Mercy G, Schiappacasse L, M. Zeverino, Maire R. Should Koos grade I vestibular schwannomas be treated early with gamma knife surgery? A subgroup analysis in a series of 190 consecutive patients. Neurochirurgie. 2014;60(6):331-331. doi:https://doi.org/10.1016/j.neuchi.2014.10.028‌
2)

Bin-Alamer O, Abou-Al-Shaar H, Peker S, Samanci Y, Pelcher I, Begley S, Goenka A, Schulder M, Tourigny JN, Mathieu D, Hamel A, Briggs RG, Yu C, Zada G, Giannotta SL, Speckter H, Palque S, Tripathi M, Kumar S, Kaur R, Kumar N, Rogowski B, Shepard MJ, Johnson BA, Trifiletti DM, Warnick RE, Dayawansa S, Mashiach E, Vasconcellos FN, Bernstein K, Schnurman Z, Alzate J, Kondziolka D, Sheehan JP. Vestibular Schwannoma Koos Grade I International Study of Active Surveillance Versus Stereotactic Radiosurgery: The VISAS-K1 Study. Neurosurgery. 2024 Nov 6. doi: 10.1227/neu.0000000000003215. Epub ahead of print. PMID: 39503441.