Human brain mapping using co-registered fUS, fMRI and ESM during awake brain surgeries: A proof-of-concept study

Accurate, depth-resolved functional imaging is key in both understanding and treatment of the human brain. A new sonography-based imaging technique named functional Ultrasound (fUS) uniquely combines high sensitivity with submillimeter-subsecond spatiotemporal resolution available in large fields-of-view. In this proof-of-concept study we show that: (A) fUS reveals the same eloquent regions as found by fMRI while concomitantly visualizing in-vivo microvascular morphology underlying these functional hemodynamics and (B) fUS-based functional maps are confirmed by Electrocortical Stimulation Mapping (ESM), the current gold-standard in awake neurosurgical practice. This unique cross-modality experiment was performed using motor, visual and language-related functional tasks in patients undergoing awake brain tumor resection. The current work serves as an important milestone towards further maturity of fUS as well as a novel avenue to increase our understanding of hemodynamics-based functional brain imaging.

P14.25 Melanoma brain metastases in the era of novel therapies: a single-center, Dutch cohort study

BACKGROUND

Until recently, patients with melanoma brain metastases (MBMs) had limited therapeutic options. With the arrival of immune checkpoint inhibitors (ICIs), targeted therapy (TT) and advances in stereotactic radiotherapy (SRT), treatment has improved. We evaluated treatments and patient outcome before and after the introduction of these novel therapies.

MATERIAL AND METHODS

In this retrospective, single-center study, patients presenting with MBMs at the Erasmus MC between November 2005 and January 2021 with sufficient follow-up were included. Overall survival (OS), measured from date of MBM diagnosis, was calculated using the Kaplan-Meier method. Patients were stratified according to MBM diagnosis before and after January 1, 2016, since novel therapies were mostly prescribed in our clinic after this date. Results were significant (p<0.05), unless otherwise stated.

RESULTS

Overall, 413 patients were included. Median [IQR] age was 56.6 years [52–71] with a 60% male predominance. A BRAF mutation was present in 46.7% of patients. A single MBM was found in 29.3% and ≥4 MBMs were found in 49.0% of patients. Before January 1, 2016, 191 patients were treated, and 222 patients after that date. Chemotherapy was more frequently used before 2016, both prior to (3.9% pre-2016 vs. 0.9% post-2016) and after (7.0% vs. 0.0%) the diagnosis of MBMs. In contrast, treatment with TT was more frequent after 2016, both prior to (3.7% vs. 16.2%) and after (7.9% vs. 41.4%) the diagnosis of MBMs. Comparable changes were observed for treatment with ICIs (prior to MBM diagnosis: 0.5% vs. 25.2%; after MBM diagnosis: 18.3% vs 39.2%). The application of SRT did not differ significantly before and after 2016 (12.0% vs. 19.4%, p=0.89), while the application of whole brain radiotherapy (WBRT) decreased (52.4% vs. 13.5%). Surgical resection was not significantly different between those periods (15.7% vs. 16.7%, p=0.90). Before 2016, median OS [IQR] was shorter than after 2016 (4.6 [1.9–10.9] vs. 6.6 [1.8–24.5] months). The effect of novel therapies on OS was further analysed in patients diagnosed after 2016; treatment vs. no treatment was compared. ICI treatment prior to MBM diagnosis was associated with worse OS (median OS 4.0 vs. 7.5 months). ICI treatment after MBM diagnosis was associated with better OS (median OS 24.5 vs. 3.0 months). In patients with a BRAF mutation, TT before MBM diagnosis was associated with worse OS (median OS 1.8 vs. 9.4 months). TT after MBM diagnosis in those patients was not significantly associated with improved OS (median OS 7.6 vs. 5.2 months, p=0.96).

CONCLUSION

Recent therapeutic advances for MBM replaced WBRT and chemotherapy with SRT, TT and ICIs. In that period, prognosis of MBM patients increased significantly. OS in patients treated with ICIs or TT prior to MBM diagnosis is still poor, but OS is improved in patients treated with ICIs after the diagnosis of MBM.

Safety and efficacy of frameless and frame-based intracranial biopsy techniques

BACKGROUND

Frameless stereotaxy or neuronavigation has evolved into a feasible technology to acquire intracranial biopsies with good accuracy and little mortality. However, few studies have evaluated the diagnostic yield, morbidity, and mortality of this technique as compared to the established standard of frame-based stereotactic brain biopsy. We report our experience of a large number of procedures performed with one or other technique.

PATIENTS AND METHODS

We retrospectively assessed 465 consecutive biopsies done over a ten-year time span; Data from 391 biopsies (227 frame-based and 164 frameless) were available for analysis. Patient demographics, peri-operative characteristics, and histological diagnosis were reviewed and then information was analysed to identify factors associated with the biopsy not yielding a diagnosis and of it being followed by death.

RESULTS

On average, nine tissue samples were taken with either stereotaxy technique. Overall, the biopsy led to a diagnosis on 89.4% of occasions. No differences were found between the two biopsy procedures. In a multiple regression analysis, it was found that left-sided lesions were less likely to result in a non-diagnostic tissue sample (p = 0.023), and cerebellar lesions showed a high risk of negative histology (p = 0.006). Postoperative complications were seen after 12.1% of biopsies, including 15 symptomatic haemorrhages (3.8%). There was not a difference between the rates of complication after either a frame-based or a frameless biopsy. Overall, peri-operative complications (p = 0.030) and deep-seated lesions (p = 0.060) increased the risk of biopsy-related death. Symptomatic haemorrhages resulting in death (1.5% of all biopsies) were more frequently seen after biopsy of a fronto-temporally located lesion (p = 0.007) and in patients with a histologically confirmed lymphoma (p = 0.039).

CONCLUSIONS

The diagnostic yield, complication rates, and biopsy-related mortality did not differ between a frameless biopsy technique and the established frame-based technique. The site of the lesion and the occurrence of a peri-operative complication were associated with the likelihood of failure to achieve a diagnosis and with death after biopsy. We believe that using intraoperative frozen section or cytologic smear histology is essential during a stereotactic biopsy in order to increase the diagnostic yield and to limit the number of biopsy specimens that need to be taken.

Pharmacology of traumatic brain injury

The intensity of experimental and clinical research to identify a neuroprotective drug for the treatment of traumatic brain injury is motivated by the devastating morbidity and mortality of this condition. Encouraging experimental work has led so far to disappointing clinical trials and the identification of new potential therapeutic targets is critically dependent on a better understanding of the chronic pathophysiology triggered by the initial insult. Future advances in the pharmacological treatment of traumatic brain injury are likely to include the evaluation of sequentially timed therapies combining multiple and targeted agents, and manipulation of the newly discovered neurogenic potential of the adult brain together with the refinement of traditional interventions to block specific cytotoxic cascades.

Serial transcranial Doppler measurements in traumatic brain injury with special focus on the early posttraumatic period

BACKGROUND

Cerebral ischemia is considered a key factor in the development of secondary damage after Traumatic Brain Injury (TBI). Studies on Cerebral Blood Flow (CBF) have documented decreased flow in over 50% of patients with TBI, studied in the acute phase. Transcranial Doppler (TCD) sonography is a non-invasive technique, permitting frequent or continuous measurements of blood flow velocity in the basal cerebral arteries.

OBJECTIVES

To investigate the potential of TCD to detect decreased blood flow velocity in the early phase after TBI;To investigate whether flow velocity differs between hemispheres in patients with focal lesions versus those with more diffuse injuries;To investigate if decreased blood flow velocity is indicative of cerebral ischemia, as evidenced by measurements of brain tissue pO(2).

METHODS

TCD examinations were performed in 57 patients with severe TBI (GCS<or=8) daily over a period of 10 days, with particular attention focused on the first 72 hours, during which period examinations were performed more frequently. A low flow velocity state (LFVS) was defined as a flow velocity<or=35 cm/sec in one or both MCA's within 72 hours after trauma. PbrO(2) was measured in 33 patients with an intraparenchymal Clark type electrode (Licox).Patients were differentiated into those with primarily unilateral pathology on the admission CT scan versus those with primarily more diffuse or bilateral pathology. Outcome was evaluated at six months after injury, according to the Glasgow Outcome Scale (GOS).

RESULTS

A low flow velocity state was observed in 63% of patients studied. Decreased flow was most pronounced during the first eight hours after injury and was accompanied by high pulsatility indices, especially at the side of the lesion. Flow velocity increased significantly after this time period. Initial Vmca values had a strong correlation with ipsilateral measured PbrO(2) values (R=0.73). The occurrence of a LFVS was associated with poorer outcome (odds ratio 3.9).

CONCLUSIONS

TCD studies show reduction of cerebral blood flow velocity in the acute phase after traumatic brain injury. Decreased flow velocity is most pronounced ipsilateral to focal pathology. A low flow velocity state is probably due to high peripheral resistance, and is indicative of ischemia, as demonstrated by the association with decreased PbrO(2). A low flow velocity state is of prognostic value and identifies patients at increased risk for ischemia. Early TCD studies are recommended in TBI.

Viscoelastic properties of bladder wall strips

Ninety-five stress-decrease curves of dog bladder strips, selected from 204 experimentally determined curves, were analyzed in terms of a model which can be described by an equation containing two or three exponential terms and a constant. As might be expected, the three-exponential equation gave the better fit. The results are discussed and compared with those derived from measurements on whole bladders. The relaxation constants determined for bladder strips agree remarkably well with those for whole bladders, indicating that the value of these constants is independent of geometry.