Astrid Jilch

Intraoperative monopolar mapping during 5-ALA-guided resections of glioblastomas adjacent to motor eloquent areas: evaluation of resection rates and neurological outcome

OBJECT Resection of glioblastoma adjacent to motor cortex or subcortical motor pathways carries a high risk of both incomplete resection and postoperative motor deficits. Although the strategy of maximum safe resection is widely accepted, the rates of complete resection of enhancing tumor (CRET) and the exact causes for motor deficits (mechanical vs vascular) are not always known. The authors report the results of their concept of combining monopolar mapping and 5-aminolevulinic acid (5-ALA)-guided surgery in patients with glioblastoma adjacent to eloquent tissue. METHODS The authors prospectively studied 72 consecutive patients who underwent 5-ALA-guided surgery for a glioblastoma adjacent to the corticospinal tract (CST; < 10 mm) with continuous dynamic monopolar motor mapping (short-train interstimulus interval 4.0 msec, pulse duration 500 μsec) coupled to an acoustic motor evoked potential (MEP) alarm. The extent of resection was determined based on early (< 48 hours) postoperative MRI findings. Motor function was assessed 1 day after surgery, at discharge, and at 3 months. RESULTS Five patients were excluded because of nonadherence to protocol; thus, 67 patients were evaluated. The lowest motor threshold reached during individual surgery was as follows (motor threshold, number of patients): > 20 mA, n = 8; 11-20 mA, n = 13; 6-10 mA, n = 10; 4-5 mA, n = 13; and 1-3 mA, n = 23. Motor deterioration at postsurgical Day 1 and at discharge occurred in 30% (n = 20) and 10% (n = 7) of patients, respectively. At 3 months, 3 patients (4%) had a persisting postoperative motor deficit, 2 caused by vascular injury and 1 by mechanical injury. The rates of intra- and postoperative seizures were 1% and 0%, respectively. Complete resection of enhancing tumor was achieved in 73% of patients (49/67) despite proximity to the CST. CONCLUSIONS A rather high rate of CRET can be achieved in glioblastomas in motor eloquent areas via a combination of 5-ALA for tumor identification and intraoperative mapping for distinguishing between presumed and actual motor eloquent tissues. Continuous dynamic mapping was found to be a very ergonomic technique that localizes the motor tissue early and reliably.

Early Re-Do Surgery for Glioblastoma Is a Feasible and Safe Strategy to Achieve Complete Resection of Enhancing Tumor

Background Complete resection of enhancing tumor as assessed by early (<72 hours) postoperative MRI is regarded as the optimal result in glioblastoma surgery. As yet, there is no consensus on standard procedure if post-operative imaging reveals unintended tumor remnants. Objective The current study evaluated the feasibility and safety of an early re-do surgery aimed at completing resections with the aid of 5-ALA fluorescence and neuronavigation after detection of enhancing tumor remnants on post-operative MRI. Methods From October 2008 to October 2012 a single center institutional protocol offered a second surgery within one week to patients with unintentional incomplete glioblastoma resection. We report on the feasibility of the use 5-ALA fluorescence guidance, the extent of resection (EOR) rates and complications of early re-do surgery. Results Nine of 151 patients (6%) with glioblastoma resections had an unintentional tumor remnant with a volume >0.175 cm3. 5-ALA guided re-do surgery completed the resection (CRET) in all patients without causing neurological deficits, infections or other complications. Patients who underwent a re-do surgery remained hospitalized between surgeries, resulting in a mean length of hospital stay of 11 days (range 7-15), compared to 9 days for single surgery (range 3-23; p=0.147). Conclusion Our early re-do protocol led to complete resection of all enhancing tumor in all cases without any new neurological deficits and thus provides a similar oncological result as intraoperative MRI (iMRI). The repeated use of 5-ALA induced fluorescence, used for identification of small remnants, remains highly sensitive and specific in the setting of re-do surgery. Early re-do surgery is a feasible and safe strategy to complete unintended subtotal resections.

Management of spontaneous intracranial hypotension – Transorbital ultrasound as discriminator

Objective Spontaneous intracranial hypotension (SIH) is most commonly caused by cerebrospinal fluid (CSF) leakage. Therefore, we hypothesised that patients with orthostatic headache (OH) would show decreased optic nerve sheath diameter (ONSD) during changes from supine to upright position. Methods Transorbital B-mode ultrasound was performed employing a high-frequency transducer for ONSD measurements in the supine and upright positions. Absolute values and changes of ONSD from supine to upright were assessed. Ultrasound was performed in 39 SIH patients, 18 with OH and 21 without OH, and in 39 age-matched control subjects. The control group comprised 20 patients admitted for back surgery without headache or any orthostatic symptoms, and 19 healthy controls. Results In supine position, mean ONSD (±SD) was similar in patients with (5.38±0.91 mm) or without OH (5.48±0.89 mm; p=0.921). However, in upright position, mean ONSD was different between patients with (4.84±0.99 mm) and without OH (5.53±0.99 mm; p=0.044). Furthermore, the change in ONSD from supine to upright position was significantly greater in SIH patients with OH (−0.53±0.34 mm) than in SIH patients without OH (0.05±0.41 mm; p≤0.001) or in control subjects (0.01±0.38 mm; p≤0.001; area under the curve: 0.874 in receiver operating characteristics analysis). Conclusions Symptomatic patients with SIH showed a significant decrease of ONSD, as assessed by ultrasound, when changing from the supine to the upright position. Ultrasound assessment of the ONSD in two positions may be a novel, non-invasive tool for the diagnosis and follow-up of SIH and for elucidating the pathophysiology of SIH.

A review of monopolar motor mapping and a comprehensive guide to continuous dynamic motor mapping for resection of motor eloquent brain tumors

Monopolar mapping of motor function differs from the most commonly used method of intraoperative mapping, i.e. bipolar direct electrical stimulation at 50-60Hz (Penfield technique mapping). Most importantly, the monopolar probe emits a radial, homogenous electrical field different to the more focused inter-tip bipolar electrical field. Most users combine monopolar stimulation with the short train technique, also called high frequency stimulation, or train-of-five techniques. It consists of trains of four to nine monopolar rectangular electrical pulses of 200-500μs pulse length with an inter stimulus interval of 2-4msec. High frequency short train stimulation triggers a time-locked motor-evoked potential response, which has a defined latency and an easily quantifiable amplitude. In this way, motor thresholds might be used to evaluate a current-to-distance relation. The homogeneous electrical field and the current-to-distance approximation provide the surgeon with an estimate of the remaining distance to the corticospinal tract, enabling the surgeon to adjust the speed of resection as the corticospinal tract is approached. Furthermore, this stimulation paradigm is associated with a lower incidence of intraoperative seizures, allowing continuous stimulation. Hence, monopolar mapping is increasingly used as part of a strategy of continuous dynamic mapping: ergonomically integrated into the surgeons tools, the monopolar probe reliably provides continuous/uninterrupted feedback on motor function. As part of this strategy, motor mapping is not any longer a time consuming interruption of resection but rather a radar-like, real-time information system on the spatial relationship of the current resection site to eloquent motor structures.

Infection rate of emergency bolt-kit vs. non-emergency conventional implanted silver bearing external ventricular drainage catheters

BACKGROUND Bolt-kit systems are increasingly used as an alternative to conventional external cerebrospinal fluid (CSF) drainage systems. Since 2009 we regularly utilize bolt-kit external ventricular drainage (EVD) systems with silver-bearing catheters inserted manually with a hand drill and skull screws for emergency ventriculostomy. For non-emergency situations, we use conventional ventriculostomy with subcutaneous tunneled silver-bearing catheters, performed in the operating room with a pneumatic drill. This retrospective analysis compared the two techniques in terms of infection rates. METHODS 152 patients (aged 17-85 years, mean=55.4 years) were included in the final analysis; 95 received bolt-kit silver-bearing catheters and 57 received conventionally implanted silver-bearing catheters. The primary endpoint combined infection parameters: occurrence of positive CSF culture, colonization of catheter tips, or elevated CSF white blood cell counts (>4/μl). Secondary outcome parameters were presence of microorganisms in CSF or on catheter tips. Incidence of increased CSF cell counts and number of patients with catheter malposition were also compared. RESULTS The primary outcome, defined as analysis of combined infection parameters (occurrence of either positive CSF culture, colonization of the catheter tips or raised CSF white blood cell counts >4/μl)was not significantly different between the groups (58.9% bolt-kit group vs. 63.2% conventionally implanted group, p=0.61, chi-square-test). The bolt-kit group was non-inferior and not superior to the conventional group (relative risk reduction of 6.7%; 90% confidence interval: -19.9% to 25.6%). Secondary outcomes showed no statistically significant difference in the incidence of microorganisms in CSF (2.1% bolt-kit vs. 5.3% conventionally implanted; p=0.30; chi-square-test). CONCLUSIONS This analysis indicates that silver-bearing EVD catheters implanted with a bolt-kit system outside the operating room do not significantly elevate the risk of CSF infection as compared to conventional implant methods.

EHMTI-0385. Dynamic ultrasound of the optic nerve sheath diameter in patients with orthostatic headaches: a new diagnostic tool in patients with spontaneous intracranial hypotension

Objective Spontaneous intracranial hypotension (SIH) caused by cerebrospinal fluid leakage commonly presents with orthostatic headache. We hypothesize that positional changes, i.e. a decrease of the optic nerve sheath diameter (ONSD) occur from supine to upright position in symptomatic patients with orthostatic headaches. We performed an ultrasound study investigating whether there are positional changes in ONSD in symptomatic patients suffering orthostatic headaches. Methods Dynamic ultrasound was performed in 44 consecutive patients with suspected SIH. In 18 patients the leading symptom was orthostatic headaches (Group A:10 men, 8 women; mean age 51.9 years), while 26 patients did not suffer from acute orthostatic headaches (Group B: 15 men, 11 women; mean age 61.9 years). Results In supine position ONSD were similar in both groups (A: mean 0.538 vs. B: 0.539cm; p = 0.957). In the upright position mean ONSD was significantly smaller in patients with orthostatic headaches (mean 0.484 ± SD 0.095cm) as compared to patients without (0.549 ± SD 0.097cm, p = 0.036). Patients with orthostatic headaches showed a larger change of ONSD from supine to upright position (mean -0.053 ± SD 0.034cm) compared to patients without orthostatic headaches (0.005 ± SD 0.038cm, p ≤ 0.001). Conclusion In this series significant changes of ONSD occurred during dynamic measurement from supine to upright patient position only in patients with acute orthostatic headaches. We call this method of comparing supine and subsequent upright ONSD “dynamic assessment of the optic nerve sheath diameter by ultrasound”. Transorbital dynamic ultrasound may become a useful, novel, non-invasive diagnostic tool for patients with orthostatic headaches. No conflict of interest.