The Yin and Yang of Operating on a Posterior Fossa Meningioma: The Schmahmann Syndrome.

The cerebellum is classically linked with control of motor function, such as coordination, balance, and regulation of movement. There is an increasing awareness, now, of the non-motor functions of the cerebellum, and the occurrence of behavioral anomalies with cerebellar disorders. We present the first report of Schmahmann syndrome (cerebellar cognitive affective syndrome [CCAS]) occurring secondary to posterior fossa meningioma excision. A 35-year-old lady with a posterior fossa meningioma developed an infarct of the right posterosuperior cerebellar hemisphere and ipsilateral superior vermis, following suboccipital craniotomy and tumor resection. Few days after the surgery, she presented with aggressive and emotional behavior, irrelevant talk, and emotional lability. The CCAS scale was administered, and she scored poorly on almost all parameters. A neuropsychological evaluation was also done. The occurrence of CCAS, posterior fossa syndrome (PFS), and behavioral abnormalities like abnormal pathological laughter/crying provides further clinical evidence of the "affective" functions of the cerebellum, modulated mainly by the posterior lobe and vermis of the cerebellum.

Intracranial Meningiomas Developed after Traditional Scalp Thermal Cautery Treatment in Childhood: Clinical Reports and Gene Expression Analysis.

BACKGROUND: Human skin cautery, a traditional thermal therapy, is traced back to Hippocrates beyond the 5th century. Those ancient healers used this method to control bleeding and infection and remove cancerous tumors. Such traditional procedure is still in practice in several regions of Asia and Africa to treat certain conditions. There is a lack of reports in the literature regarding the long-term complication and the possible tumorigenesis following traditional treatment with thermal cauterization. Here, we report two patients with intracranial meningiomas and investigate the gene expression profile for a patient. Cases presentations: We report two adult patients who presented with a headache and hemiparesis over six months. Brain magnetic resonance imaging (MRI) scans of both patients revealed intracranial meningiomas. During preoperative preparation of the patients, cautery marks were noticed over the scalp region above the intracranial tumors site, which was performed during childhood. The patients underwent uneventful resection of meningiomas with no local recurrence over a 5-year follow up. In addition, we performed a biofunctional genetic microarray expression analysis on the affected meningioma. CONCLUSION: There is a lack of evidence-based scientific reports in the literature regarding the long-term complications and tumorigenesis following aggressive treatment with thermal cauterization. Herein, we report the first possible association between previous scalp traditional cautery and the development meningioma in two patients and discuss a proposed causal relationship. However, further advanced studies and research should be done to support, or reject, our hypothesis.

Pleural metastasis of atypical meningioma: a novel therapeutic approach.

Meningiomas are the most common intracranial tumours in adults and they are infrequently associated with a metastasis clinical course. Pleural metastases are extremely rare and no guidelines on a specific treatment have been established. When localized, surgical resection is the mainstay of treatment, but there is a high risk of pleural recurrence. We aimed to describe a novel surgical approach in pleural metastasis of meningiomas. We report the case of a 41-year-old man with the medical history of surgically resected intracranial atypical meningioma. Nine years after diagnosis of atypical meningioma, a CT scan of the chest disclosed 10 pleural implants gathered in the fissure, in the paramediastinal pleura and at the base of the left hemithorax. Surgical resection was decided. Parietal and mediastinal pleura resection with visceral pleural lesions removal were performed. Cytoreductive surgery was associated with intrathoracic hyperthermic chemotherapy. Postoperative course was uneventful and no adjuvant therapy was undertaken. The patient is free of pleural recurrence 12 months post operatively. The present case report suggests that cytoreductive surgery with intrathoracic hyperthermic chemotherapy is feasible and safe in pleural metastasis from meningioma. Prolonged follow-up and prospective studies are mandatory to assess its oncological benefit.

Laser Interstitial Thermotherapy for Treatment of Symptomatic Peritumoral Edema After Radiosurgery for Meningioma.

BACKGROUND: Symptomatic peritumoral edema (PTE) is a known complication after radiosurgical treatment of meningiomas. Although the edema in most patients can be successfully managed conservatively with corticosteroid therapy or bevacizumab, some medically refractory cases may require surgical resection of the underlying lesion when feasible. Laser interstitial thermotherapy (LITT) continues to gain traction as an effective therapeutic modality for the treatment of radiation necrosis where its biggest impact is through the control of peritumoral edema. CASE DESCRIPTION: A 56-year-old woman with neurofibromatosis 2 presented with a symptomatic, regrowing left frontotemporal lesion that had previously been radiated, then resected with confirmed recurrence of grade I meningioma, and subsequently radiated again for lesion recurrence. Given her history of 2 prior same-side craniotomies, including a complication of wound infection, she was not a candidate for further open surgical resection. Having failed conservative management, she underwent LITT with intraoperative biopsy demonstrating viable grade I meningioma. Postoperatively, she demonstrated radiographic marked, serial reduction of PTE and experienced resolution of her symptoms. CONCLUSIONS: This case demonstrates that LITT may be a viable alternative treatment for patients with meningioma with symptomatic PTE who have failed medical therapy and require surgical intervention.

Acupuncture for rehabilitation after surgery for cerebellopontine angle meningioma: A case report.

RATIONALE: In some cases, surgery of cerebellopontine angle meningioma (CPAM) might result in multiple cranial nerve injury, which could bring serious impact on the patients, especially when it affects the function of facial muscles and eyeballs. This report describes a successful application of acupuncture for rehabilitation in a patient after surgery for CPAM. PATIENT CONCERNS: A 27-year-old patient presented with limitation of left eye abduction, accompanied with frontal and facial sensory disturbance on the left after resection of the pontocerebellar angle tumor. The patient also suffered from significant anxiety and depression as concomitant symptoms. DIAGNOSES: Based on medical history, clinical symptoms, and magnetic resonance imaging results, the patient was diagnosed with the fourth, fifth, sixth, and seventh cranial nerve injury after surgery for CPAM. INTERVENTIONS: Acupuncture treatment was applied for this patient. One acupuncture session was given every 2 days in 35 days, and the needles were retained for 30 minutes per session. OUTCOMES: After acupuncture treatment, the limitation of left eye abduction had totally recovered. The superficial sensory disturbance in the frontal and facial region was significantly relived. Besides, the scores of Hamilton Anxiety and Depression Scale showed a significant reduction. However, the superficial sensory of the alar and nasolabial groove on the left side still decreased mildly when compared with the right side. CONCLUSION: Acupuncture might be an option for rehabilitation after surgery for CPAM.

Brachytherapy as an Adjuvant for Recurrent Atypical and Malignant Meningiomas.

BACKGROUND: Recurrent atypical and malignant meningiomas have poor outcomes with surgical therapy alone. Neither adjuvant chemotherapy nor postoperative radiation therapy remedies this problem. OBJECTIVE: To evaluate our experience with the treatment of 15 patients treated with I-125 or Cs-131 brachytherapy radiation seeds as an adjuvant in these difficult cases. METHODS: Patients with high-grade recurrent meningioma who underwent resection and intraoperative placement of brachytherapy seeds at our institution from 2002 to 2014 were identified and studied by retrospective chart review. RESULTS: Fifteen patients with median age of 68.8 yr were treated with I-125 (n = 13) or Cs-131 (n = 2) brachytherapy seeds for cases of recurrent, grade II (n = 8), or grade III (n = 7) meningioma at our institution from 2002 to 2014. These lesions originated from a variety of locations including, convexity (3), falcine (3), frontal (2), occipital (1), parietal (2), 2 sphenoid wing (2), and temporal (2), based recurrent meningiomas. Patients had a median of 2 prior open surgical interventions and received local radiation therapy with a median dose of 55 Gy prior to brachytherapy. Survival at 2.5 yr was 56% for grade II and 17% for grade III lesions. Survival was significantly associated with patient age but not tumoral pathology. Forty percent of patients required reoperations for wound complications following brachytherapy. CONCLUSION: Brachytherapy with implantation of permanent radiation seeds provides a viable alternative treatment for recurrent meningioma while carrying a significant clinical risk of wound infection and need for reoperation.

Transsphenoidal versus Transcranial Approach for Treatment of Tuberculum Sellae Meningiomas: A Systematic Review and Meta-analysis of Comparative Studies.

There is controversy regarding the surgical route selection for tuberculum sellae meningiomas (TSMs): the transsphenoidal (TS) or transcranial (TC) approach? We conducted a systematic review and meta-analysis to compare clinical outcomes and postoperative complications between two surgical approaches. Literature search was performed. Relevant articles were selected and evaluated. Data were extracted and analyzed. Eight articles comprising 550 patients met the inclusion criteria. Traditionally, the rates of gross total resection, tumor recurrence, visual improvement, and cerebrospinal fluid leakage were the most common outcomes of interest. We demonstrated that the TS approach was significantly associated with better visual outcomes but more frequent cerebrospinal fluid leakage, while the rates of tumor resection and recurrence showed no significant difference between groups. In addition to surgical results that were consistent with previous studies, we further evaluated the impact of approach selection on common postoperative complications, which were closely related to the recovery course and quality of life. We revealed that the risk of dysosmia was significantly higher in the TS group. There was no significant difference between groups regarding infection, intracranial hemorrhage, and endocrine disorders. Because of the relatively low evidence levels of included retrospective studies, it was difficult to reach a categorical conclusion about the optimal surgical approach for TSMs. Finally, we recommended that the TS approach was an alternative option in patients with smaller TSMs (<30 mm) and limited invasion of optic canals in experienced neurosurgical centers.

Soft tissue grafts for dural reconstruction after meningioma surgery.

The meninges are involved in various pathologies and are often directly or indirectly severed during surgical procedures, especially the dura mater. This can pose a real challenge for the surgeon, as a proper reconstruction of the meninges is important to prevent complications such as cerebrospinal fluid leak (CSF). A variety of techniques for dural reconstruction have been described, employing natural and artificial materials. A novel technique for dural reconstruction involves soft tissue grafts in the form of fibrous or fibromuscular flaps, which are placed on the dural defects to seal the gaps. These soft tissue grafts represent an appropriate scaffold for cell ingrowth and fibrosis, thus preventing CSF. In this pilot study, we described the application of soft tissue grafts for dural reconstruction in 10 patients who underwent convexity meningioma surgery.

Pathologic Laughter as an Early and Unusual Presenting Symptom of Petroclival Meningioma: a Case Report and Review of the Literature.

BACKGROUND: Pathologic laughter is inappropriate, involuntary, and unmotivated laughter episodes that may or may not be associated with mirth or amusement. Although associated with many diffuse brain pathologies, its association with intracranial focal mass lesions causing ventrolateral brainstem compression, like petroclival meningioma, is very rare. The exact pathophysiology of this interesting and unusual clinical symptom is unknown, but probably involves disinhibition and release of the so-called coordination center located in the upper brainstem due to compression by the tumor. CASE DESCRIPTION: A 26-year-old woman presented with recurrent episodes of inappropriate and involuntary laughter, which significantly affected her quality of life, for 2 years. These episodes did not resolve, and a magnetic resonance imaging of the brain showed a giant petroclival meningioma causing upper brainstem compression. Near-total excision of the tumor was done using an extended middle fossa approach. To our surprise, the pathologic laughter subsided immediately after surgery. CONCLUSIONS: Pathologic laughter may be the only symptom of a focal mass lesion causing ventrolateral upper brainstem compression, like petroclival meningioma, well before other neurological sign/symptoms appear. Tumors causing ventral brainstem compression must be ruled out before the patient is sent for a psychiatric evaluation.

Systemic Rosai-Dorfman disease with central nervous system involvement.

Rosai-Dorfman disease (RDD) is a rare idiopathic and lymphoproliferative disorder. Central nervous system (CNS) involvement is infrequent and typically manifests as an isolated lesion. In this article, we describe an unusual case of RDD with multiple lesions in the CNS, upper respiratory tract and lymph nodes. A literature review revealed 45 cases (including the one described herein) of systemic RDD with CNS involvement documented to date. Among these cases, 29 (64.4%) presented with intracranial lesions, 10 (22.2%) with spinal lesions and 6 (13.3%) with both. While the condition of most patients was stable, only four died from RDD or for other reasons. Prognosis is good for most patients, even those with extensive lesions. Although there are various treatments for RDD, surgery is preferred. Given the rarity of RDD, multicenter international collaborations are advocated in order to study disease pathogenesis and develop effective treatment strategies.

Coagulation in hindbrain membrane meningioma patients treated with different injections using acute hypervolemic hemodilution.

The aim of this study was to analyze the changes in coagulation in meningioma patients treated with different injections using the method of acute hypervolemic hemodilution (AHH). One hundred fifty hindbrain membrane meningioma patients were randomly divided into 5 groups, 30 per group. The first group were injected 40ml/time with Danhong after anesthesia induction; the second group were injected with 40ml~60ml/time Kangai and combined with interventional chemotherapy and embolization procedure; the third group of AHH were injected with polygeline 15ml/kg; the fourth group were injected with hydroxyethyl starch (130/0.4) sodium chloride in doses of 15ml/kg; the control group underwent basic treatment for lowering blood pressure and lowering blood fat. The changes of coagulation index were recorded before and after surgery and before and after the injection of different medications. Compared to the control group, for the first group of AHH, after being treated for 10 days and 30 days, the concentrations of bone specific alkaline phosphatase (BALP), bone Gla protein (BGP) and pro-collagen carboxy-terminal propeptide (PICP) were higher than that of the control group, the levels of endotoxin (ET) and C-reactive protein (CRP) were decreased compared to the control group (p less than 0.05); for the second group of AHH, after being treated for 10 days, the index of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (Fg) were not significantly changed, but the related level of vascular endothelial growth factor (VEGF) significantly decreased (p less than 0.05). Comparing the coagulation function index after surgery in the third and fourth groups, there were no significant changes in mean arterial pressure (MAP) level, heart rate (HR) value presented a low decrease, central venous pressure (CVP) level increased and the level of interleukin IL-6 showed a steady state after increasing. Analyzing the levels of interleukin IL-8 and tumor necrosis factor-α (TNF-α) after surgery, it was seen that in the third group they increased and in the fourth group they decreased (p less than 0.05). Danhong injection improved the coagulation function and microcirculation of patients, Kangai injection and interventional chemotherapy and embolization restrained the appearance of tumor angiogenesis, AHH operation with polygeline injection and hydroxyethyl starch (130/0.4) sodium chloride kept blood flow in normal parameters.

The impact of peri-operative dexamethasone administration on the normal hypothalamic pituitary adrenal response to major surgical procedures.

BACKGROUND: Surgical procedures are associated with activation of the hypothalamic-pituitary-adrenal axis (HPA). Studies examining HPA dynamics peri-operatively are limited and the modulating influence of peri-operatively administered glucocorticoids on that is not well established. This investigation examined alterations in HPA function and the impact of dexamethasone (DEX) administration during the peri-operative period. METHODS: We examined HPA function in 297 patients with normal function who had surgical procedures including pituitary mass resection (n = 191), craniotomy (n = 17) and other thoracic/ abdominal/ pelvic surgeries (n = 89). HPA function was assessed by frequent measurements of parameters defining adrenal function: ACTH, cortisol, DHEA and DHEA-S levels for 48 h. DEX was administered as a single dose (2-10 mg) to 30 and as multiple doses (12-36 mg) to 21 patients. The data of DEX-treated subjects within each group were similar and were combined together. RESULTS: Pre-operative data were similar for patients having different surgical procedures. Without DEX exposure, ACTH increased to 225 ± 100 ng/L at 2-4 h and gradually declined to baseline values by 36 h while cortisol levels peaked (39.2 ± 13.2 ug/dL) at 6-8 h declining gradually thereafter. Cortisol rise was paralleled by an equimolar increase in DHEA and a subsequent increase in DHEA-S levels. Single doses of DEX did not influence ACTH or cortisol secretion but suppressed the expected rise in DHEA and DHEA-S levels. Multiple doses of DEX suppressed ACTH and cortisol after the 15th postoperative hour and completely blocked the expected rise in DHEA and DHEA-S levels. CONCLUSIONS: The data provide a detailed overview of HPA function in a large number of subjects who had major surgical procedures. Single and large doses of DEX did not suppress ACTH or cortisol secretion but suppressed adrenal androgen secretion. It took multiple doses of DEX to partially suppress ACTH and cortisol secretion in the peri-operative period.

Prospective analysis of neuropsychological deficits following resection of benign skull base meningiomas.

OBJECTIVE Resection of skull base tumors is challenging. The introduction of alternative treatment options, such as radiotherapy, has sparked discussion regarding outcome in terms of quality of life and neuropsychological deficits. So far, however, no prospective data are available on this topic. METHODS A total of 58 patients with skull base meningiomas who underwent surgery for the first time were enrolled in this prospective single-center trial. The average age of the patients was 56.4 ± 12.5 years. Seventy-nine percent of the tumors were located within the anterior skull base. Neurological examinations and neuropsychological testing were performed at 3 time points: 1 day prior to surgery (T1), 3-5 months after surgery (T2), and 9-12 months after surgery (T3). The average follow-up duration was 13.8 months. Neuropsychological assessment consisted of quality of life, depression and anxiety, verbal learning and memory, cognitive speed, attention and concentration, figural memory, and visual-motor speed. RESULTS Following surgery, 23% of patients showed transient neurological deficits and 12% showed permanent new neurological deficits with varying grades of manifestation. Postoperative quality of life, however, remained stable and was slightly improved at follow-up examinations at T3 (60.6 ± 21.5 vs 63.6 ± 24.1 points), and there was no observed effect on anxiety and depression. Long-term verbal memory, working memory, and executive functioning were slightly affected within the first months following surgery and appeared to be the most vulnerable to impairment by the tumor or the resection but were stable or improved in the majority of patients at long-term follow-up examinations after 1 year. CONCLUSIONS This report describes the first prospective study of neuropsychological outcomes following resection of skull base meningiomas and, as such, contributes to a better understanding of postoperative impairment in these patients. Despite deterioration in a minority of patients on subscales of the measures used, the majority demonstrated stable or improved outcome at follow-up assessments.

Intraoperative aberrant bispectral index values due to facial nerve monitoring.

Bispectral index is an accepted depth of anaesthesia monitor for guiding intraoperative hypnotic agent administration. Frontalis EMG displayed on BIS monitor may increase due to twitching of frontalis muscle. EMG increases are also known to cause artefactual increases in BIS values. We report a case of artefactual increase of EMG and subsequently BIS values, due to electrical artefact from cranial nerve stimulator being used to identify the facial nerve. An explanation of the effect of stimulator signal on BIS EMG and BIS values has been provided.

Behavioural improvement in a minimally conscious state after caloric vestibular stimulation: evidence from two single case studies.

OBJECTIVE: To investigate whether caloric vestibular stimulation, a non-invasive form of neuro-modulation, alters the level of awareness in people residing in a minimally conscious state. DESIGN: Single-case ( n = 2), prospective, controlled (ABAB) efficacy study. SETTING: Tertiary, neuro-rehabilitation inpatient ward within a university hospital. PARTICIPANTS: Two individuals in a minimally conscious state. INTERVENTION: Left ear caloric vestibular stimulation was performed in two four/five-week blocks interleaved with two four/five-week blocks of sham stimulation. Session duration and frequency gradually increased within each block from once per day for 10 minutes (Week 1) to once per day for 20 minutes (Week 2) to 20 minutes twice per day in the remaining weeks. MEASURES: Wessex Head Injury Matrix, JFK Coma Recovery Scale - Revised. RESULTS: Both participants' Wessex Head Injury Matrix scores indicated a transition from involuntary (i.e. mechanical vocalization) to voluntary (i.e. gesture making, selective responses to family members) behaviour that was time-locked to the onset of active stimulation. In one participant, this improvement persisted for at least four weeks after active stimulation, while in the other it diminished two weeks after stimulation. Allied, although less dramatic, changes were seen on the arousal and auditory subscales of the JFK Coma Recovery Scale - Revised. CONCLUSION: The data provide the first evidence that vestibular stimulation may help improve outcome in a low awareness state, although further studies are needed to replicate effect and determine longer-term benefit.

Surgical Resection and Interstitial Iodine-125 Brachytherapy for High-Grade Meningiomas: A 25-Year Series.

BACKGROUND: Atypical and malignant meningiomas can recur despite resection and radiation. OBJECTIVE: To determine outcomes of patients with recurrent atypical or malignant meningioma treated with repeat resection and permanent iodine-125 ( 125 I) brachy-therapy. METHODS: Charts of patients who underwent surgical resection and 125 I brachyther-apy implantation for atypical and malignant meningiomas between 1988 and 2013 were retrospectively reviewed. The Kaplan-Meier actuarial method was used to calculate progression-free and overall survival. The log-rank test was used to compare groups. Significance was set at P < .05. RESULTS: Forty-two patients underwent 50 resections with 125 I brachytherapy im-plantations. All patients had undergone previous resections and 85% had previously undergone radiation. Median follow-up was 7.5 years after diagnosis and 2.3 years after brachytherapy. Median time to progression after resection with 125 I brachytherapy was 20.9 months for atypical meningioma, 11.4 months for malignant meningioma, and 11.4 months for the combined groups. Median survival after re-resection and 125 I brachytherapy was 3.5 years for atypical meningioma, 2.3 years for malignant menin-gioma, and 3.3 years for all subjects. Median overall survival after diagnosis was 11.1 years for atypical meningioma, 9.1 years for malignant meningioma, and 9.4 years for all subjects. Complications occurred in 17 patients and included radiation necrosis (n = 8, 16%), wound breakdown (n = 6, 12%), hydrocephalus (n = 4, 8%), infection (n = 3, 6%), and a pseudomeningocele (n = 2, 5%). CONCLUSION: This is the largest experience with adjuvant 125 I brachytherapy for recurrent high-grade meningiomas. The outcomes support the use of adjuvant brachytherapy as an option for these aggressive tumors.

Craniotomy for perisellar meningiomas: comparison of simple (appropriate for endoscopic approach) versus complex anatomy and surgical outcomes.

OBJECTIVE Microsurgical resection of perisellar meningiomas has remained the gold standard for treatment, with extended endoscopic endonasal surgery emerging as a viable alternative. Historical microsurgical series do not distinguish based on tumor anatomy, but are being used as a comparison against endonasal surgery. In this study, the authors retrospectively reviewed and compared the anatomy of perisellar meningiomas seen at their institution. The tumors were separated into 2 groups based on whether they would be appropriate for endoscopic resection, and the authors compared the surgical outcomes. METHODS Between 2001 and 2013, 53 patients (73.6% women) with perisellar meningiomas underwent open microsurgical resection at Vancouver General Hospital performed by the senior author (R.A.). These tumors were separated into 2 groups based on their anatomy, and the authors analyzed the resection rates, surgical results, patient quality of life, and complications. RESULTS Among the 53 patients who presented with perisellar meningiomas, the authors were able to identify 18 lesions with "simple" anatomy suitable for endoscopic resection and 35 lesions with "complex" anatomy suitable for craniotomy resection. The mean age of patients in the study cohort was 57.4 years (range 33-91 years), and most patients presented with visual loss (68.0%) and visual field restriction (64.2%). There were no major differences in patient demographic data between the 2 groups. Patients with simple anatomy had smaller lesions (2.1 vs 3.5 cm; p = 0.004), no optic canal invasion (89% vs 26%; p < 0.0001), minimal vascular encasement (cortical cuff 83% vs 9%; p < 0.0001), and a rounded tumor shape (100% vs 31.8%; p = 0.0001) when compared with those with complex anatomy. The majority of lesions originated from the tuberculum sellae and planum sphenoidale. A greater degree of resection was achieved in the favorable anatomy group (99% vs 87.1%; p < 0.0001). Vision was improved or normalized in 96.6% of patients. Patients in the cohort with complex anatomy had more transient complications; there were no incidents of surgical-site infection, meningitis, or death in this series. One patient who underwent removal of a recurrent lesion experienced a CSF leak that required endoscopic repair. The overall persisting complications rate was higher in the group with complex anatomy (11.1% vs 37.1%; p = 0.0498); overall, 28.3% of patients experienced disabling complications. Patient-perceived quality of life improved in the simple anatomy group following surgery (ΔSF-36 +16.6 vs -8.4; p = 0.0045). CONCLUSIONS Extended endoscopic surgery is emerging as a viable alternative to microsurgical resection of perisellar meningiomas. The authors identified 2 patient groups based on tumor anatomy, with distinctly separate surgical outcomes. In the future, patients considered for endoscopic resection should be compared against the surgical group with simple anatomy that includes smaller tumors, no vascular encasement, and limited optic canal invasion.

Towards an optimal paradigm for intraoperative auditory nerve monitoring with auditory steady state responses.

Auditory steady state responses (ASSR) may offer an alternative to brainstem auditory evoked potentials for monitoring of the auditory nerve during surgical procedures. In the current study, we evaluated the influence of noise on ASSR characteristics in total intravenous anesthesia (TIVA). Simulated ASSR in real noise recorded during surgery under TIVA were constructed with known parameters. Influence of amplitude, modulation frequency, averaging sweeps and detection threshold on ASSR were evaluated. High amplitude, more sweeps and a liberal threshold facilitated detection. High amplitude ASSR (80 nV) were detected in up to 45 % with 16 s of data, in 80-90 % with 112 s. Near-threshold ASSR were detected in 0.8-25 %. False positives ranged between 0.3 and 10.3 %. Number of sweeps did not influence false positives. Amplitude errors varied between -61 and +39 % and improved with more averages but not with different thresholds. Modulation rate demonstrated the strongest influence on all parameters. 110 Hz yielded best, 90 Hz the worst results. Choice of parameters strongly influences detection and characteristics of ASSR. Optimal parameters enabled detection after 16 s in 45 %. Due to specific noise characteristics, modulation has a critical impact, which is currently not sufficiently recognized in ASSR studies.