Confocal neurolasermicroscopy in human brain - perspectives for neurosurgery on a cellular level (including additional comments to this article).

BACKGROUND: During neurosurgery intraoperative imaging of vital neural structures on a cellular level would facilitate the development of new strategies for diagnosis and treatment. In vivo imaging would permit the detection of the tumour centre and infiltration zone. With targeted biopsies the lesion of interest could be determined before performing the biopsy, facilitating the final pathological diagnosis. In this study we present confocal neurolasermicroscopy as a new method in neurosurgery. METHODS: A miniaturised confocal neurolasermicroscope (NLM) was used ex vivo immediately after tumour resection of glioblastoma multiforme (GBM). NLM was performed with subcellular magnification up to a tissue depth of 100 microm. NLM images were compared to conventional histological images of the same tumour. RESULTS: The application of the method in nine patients allowed adequate diagnosis of a malignant glioma fulfilling the WHO criteria when compared to conventional histology. In one patient with glioblastoma multiforme NLM allowed the correct diagnosis of GBM to be made, demonstrating the high mitotic rate and cell pleomorphy of the tumour cells. Additional characteristics such as pleomorphic cells, mitotic figures, fibrillary matrix and the distinction between tumour centre and infiltration zone could be shown. CONCLUSIONS: NLM is a tool which could be adapted for neurosurgical intraoperative applications with the potential to diagnose tumours and recognise the tumour centre and infiltration zone in vivo. Further applications of NLM to characterise subcellular structures and vascular architecture are possible.

Does routine transcranial duplex ultrasound heat up the patient brain?

PURPOSE: The effect of transcranial duplex ultrasound (US) on the intraventricular temperature in patients was analyzed. Temperature increases during examination have been identified as a potential risk factor but only data from model studies is currently available. MATERIALS AND METHODS: Patients who had an intracranial pressure/temperature transducer implanted and underwent US assessment were included. In an examination series (B-mode, combined B- and color mode, combined B- and color mode plus Doppler, 3 min for each mode), the intracranial thermodilution thermistor was focused while intraventricular temperature and body temperature (bladder catheter or rectal probe) were recorded continuously and temperature changes were analyzed. RESULTS: Thirty-one US examinations were performed in 14 patients. Twenty-six examinations in 9 patients in which the intracranial temperature probe was depicted were included. Initial patient temperatures ranged from 35.1dgC to 38.7dgC. No significant increase or decrease in intracranial temperature was seen after the first (B-mode), second (B- and color mode) and third (B- and color mode plus Doppler) duplex US examination. T-test for paired samples showed a constant temperature throughout US examination (two-sided significance: 1.000, 1.000, 0.731). CONCLUSION: Routine transcranial duplex ultrasound does not increase the intracranial temperature in patients.

The enigma of underdrainage in shunting with hydrostatic valves and possible solutions.

OBJECTIVE: Hydrostatic devices have considerable advantages compared to "conventional" differential-pressure-valves concerning overdrainage, but are thought to imply a tendency to underdrain or to clog. The aim of this study was to evaluate the ability of the hydrostatic gravitational Dual-Switch-Valve (DSV) to minimize overdrainage-related complications without increasing the danger of underdrainage. RESULTS: In a series of 202 adult patients with different etiologies treated with a ventriculo-peritoneal shunt including the hydrostatic Dual-Switch-valve (DSV), 21 cases were suspected of suffering from underdrainage. Using a new algorithm we were able to differentiate obstruction in 6 patients from functional underdrainage in 15 cases, thus we saw an indication to reimplant a DSV with a lower opening pressure in the latter. CONCLUSION: The reasons for functional underdrainage were multifold in our series, especially the intraperitoneal pressure is still a "black box". Despite the ability of the DSV to avoid clogging and to minimize overdrainage by its high-pressure-chamber, it remains difficult to determine the optimal opening pressure of the low-pressure-chamber of the DSV for ideal clinical improvement. Therefore a new hydrostatic gravitational "programmable" valve (proGAV), entitled on avoiding the disadvantages of other adjustable devices, has been developed and implanted in 16 patients with promising results.

Tuning in caudal fastigial nucleus units during natural and galvanic labyrinth stimulation.

Neurons of the caudal fastigial nucleus were investigated by means of single unit recordings. Natural vestibular stimuli were applied as well as galvanic labyrinth polarization. One-third of the neurons showed a convergence of vertical and horizontal canals. More than 80% of the neurons responded to polarization of both the ipsilateral and contralateral canals (binaural responders). Most neurons had a limited response range. Two classes of neurons could be distinguished: up to 1 Hz responders and up to 10 Hz responders. In addition a group of fastigial cells showed a tuning within a small range of frequencies (sharp-tuning responders).