PubMed Health⌕ Search

Biomedical subjects

J Kuchta

Publications and source records attributed to J Kuchta.

13 recordsLinked to original sources
PubMed2004

Visually evoked changes of blood flow velocity and pulsatility index in the posterior cerebral arteries: a transcranial Doppler study.

OBJECTIVE: Transcranial Doppler sonography (TCD) can detect visual evoked blood flow responses non-invasively and continuously with high temporal resolution. While the mean flow velocity response to visual stimuli is well documented, the response of the pulsatile characteristics of the waveform is less well known. METHOD: We examined the changes of blood flow velocity and pulsatility index (PI) in the posterior cerebral artery (PCA) in 50 healthy volunteers. TCD responses were measured in response to metabolic activation of the visual cortex by visual stimulation. RESULTS: A specific, stimulus-related increase of the mean flow velocity (MFV) in the PCA was found. The intensity of the blood flow response was significantly influenced by the complexity of the stimulus. During complex visual stimulation we found a mean flow velocity (MFV) increase of 29.4 % from the baseline in the subjects. However, a stimulus-related decrease was observed in the pulsatility index (PI); although the mean PI with closed eyes during baseline measurement was 1.18 (SD 0.27), on average, it fell significantly to 0.95 (SD 0.23) with the alternating chessboard and 0.82 (SD 0.22) during the complex stimulus condition. The relative decrement of the pulsatility index with increasing complexity of the visual stimulus is highly significant, with values of -19.5 % and -30.5 % compared to the baseline. CONCLUSION: These findings demonstrate the inverse correlation between MFV response and pulsatility index in the PCA. We assume that this decrease of the PI in the PCA may reflect the reduced regional vascular resistance in the visual cortex during visual stimulation.

Adult↗
PubMed2004

Neuroprosthetic hearing with auditory brainstem implants.

The auditory brainstem implant (ABI) does provide auditory sensations, recognition of environmental sounds and aid in spoken communication in about 300 patients worldwide. It is no more an investigative device but widely accepted for the treatment of patients who have lost hearing due to bilateral tumors of the hearing nerve who transmits the acoustic information from the cochlea to the brain. Most of the implanted patients are completely deaf when the implant is switched off. In contrast to cochlear implants, only few of the implanted patients achieve open-set speech recognition without the help of visual cues. On average, the ABI improves communicative functions like speech recognition at about 30% when compared to lip-reading only. The task for the next years is to improve the outcome of ABI further by developing new less invasive operative approaches as well as new hardware and software for the ABI device.

Auditory Brain Stem Implants↗
PubMed2003

Acute demyelination: diagnostic difficulties and the need for brain biopsy.

BACKGROUND: Despite the rapid development in neuro-imaging over the past two decades, ring like contrast-enhancing lesions on CCT or MRI still may pose a diagnostic challenge. The main differential diagnoses of these lesions include metastatic carcinoma, high-grade glioma and brain abscess. Acute demyelination seldom turns out to be the underlying pathology. METHOD: Retrospective analysis was done on six patients with acute demyelination treated at our neurosurgical department between 1990 and 2001. Clinical, radiological, PET, intra-operative and histological findings were evaluated. FINDINGS: In five patients, the diagnosis of acute demyelination was established by histopathological evaluation of stereotactic biopsy specimen, in the sixth patient following microsurgical extirpation of the lesion. Neuropathology revealed demyelination with the presence of myelin-phagocytosing macrophages. In addition, lymphocytic infiltrates were present. Symptoms and signs improved significantly after high-dose steroid therapy. CONCLUSIONS: Despite CNS tissue destruction, necrosis and cyst formation are not usually found in demyelinating disease, being rather more common in young patients with ring-like contrast-enhancing lesions on CCT and MRI. Though an incorrect diagnosis can lead to a potentially fatal therapeutic intervention, histological diagnosis should be made in all cases. Due to minimum morbidity, stereotactic biopsy is the method of choice to obtain representative specimens for histological diagnosis. Open microsurgery of these lesions is not indicated since conservative medical treatment with steroids results in a favourable outcome in most cases.

Acute Disease↗
PubMed2002

Rehabilitation of hearing and communication functions in patients with NF2.

Most patients with neurofibromatosis type 2 (NF2) lose hearing either spontaneously or after removal of their neurofibromas. The patient may benefit from conventional hearing aids if, due to modern microsurgery and intraoperative monitoring the integrity of the cochlea and the 8th nerve is preserved. With lost auditory function but preserved electrical stimulibility of the 8th nerve a cochlear implant may be appropriate. But if the patients have no remaining 8th nerve to stimulate, there is no benefit from cochlear implants. Until some years ago, vibrotactile aids, lip-reading, and sign language have been the only communication modes available to these patients. With auditory brain stem implants it is now possible to bypass both the cochlea and the 8th nerve and to stimulate the cochlear nucleus directly. Stimulation of the devices produces useful auditory sensations in almost all patients. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores and the ability to converse on the telephone. Also lip-reading is significantly improved with brain stem implants. The successful work of an auditory brainstem program center depends very much on the close interdisciplinary collaboration between the Departments of Neurosurgery and ENT-surgery. In the future new developments like speech processing strategies and new designed electrodes accessing the complex tonotopic organization of the cochlear nucleus may further improve rehabilitation in these patients who would have been deaf some years ago.

Auditory Pathways↗
PubMed1999

Operative treatment of tentorial herniation in herpes encephalitis.

Herpes simplex virus is the most common cause of acute viral encephalitis in children. Due to the variety of possible clinical manifestations the diagnosis is often overlooked in the early stages of the disease. Anti-viral therapy with acyclovir should be started whenever HSE is suspected. When there is further deterioration under virostatic therapy, a brain biopsy should be performed to verify the diagnosis. But even when the adequate medical therapy is established, massive brain edema and brain shift resulting in tentorial herniation can develop. Up to now the reported mortality of these patients is still around 30%. Here we report on a child with severe necrotizing herpes simplex encephalitis who developed severe tentorial herniation due to a right-sided mass lesion. The patient's status markedly improved after decompressive anterior temporal lobe resection. To our knowledge a similar case has not yet been reported in the literature. We suggest that anterior temporal lobe resection and decompressive craniotomy is of benefit in selected cases with tentorial herniation because both decompression and reduction of infectious material can be achieved.

Acyclovir↗
PubMed1999

Invasive cutaneous squamous cell carcinoma associated with actinic keratosis: a case with orbital invasion and meningeal infiltration.

BACKGROUND: It is suggested that most squamous cell carcinomas in sun-exposed areas arise from preexisting solar keratosis. Actinic keratosis is thought of as being a precursor to squamous cell carcinoma. This form of squamous cell carcinoma has been considered to be a relatively benign lesion. We report a case of invasive squamous cell carcinoma associated with actinic keratosis leading to orbit destruction and meningeal infiltration. OBJECTIVE: To demonstrate that well-differentiated tumors can act extremely aggressively with the potential toward infiltrative growth patterns. METHODS: Histologically controlled surgery along with multiple radiation therapy was performed. RESULTS: The tumor progressed inducing perineural invasion, orbit infiltration, osseous destruction, and meningeal invasion. CONCLUSION: The association of squamous cell carcinoma and actinic keratosis supports the concept of a causal relation. Excision with histologic examination of actinic keratosis seems to be useful for accurate diagnosis. Squamous cell carcinoma can represent an aggressive tumor with infiltrative growth pattern and should not be considered a benign lesion.

Aged↗
PubMed1998

Delayed hearing loss after microvascular decompression of the trigeminal nerve.

OBJECTIVE: The development of sudden postoperative hearing loss as a complication of microvascular decompression (MVD) operations in the cerebellopontine angle has already been reported. A sudden hearing loss of vascular origin may also occur hours or days after such operations, but even in such cases an improvement of hearing over the following weeks is possible. Here we report on a gradual deterioration of hearing over a period of two weeks after MVD which has not been described in the literature up to now. CLINICAL PRESENTATION: A MVD operation was performed twice on a 36 year old patient with trigeminal neuralgia. After the second operation the patient developed a slight hearing impairment 3 days postoperatively which increased over a period of two weeks and ended up with total deafness. The course of intra-operative brainstem auditory evoked potentials and postoperative audiograms is documented. CONCLUSION: Because of gradual development of the delayed hearing loss, we conclude that postoperative tissue scarring may be the underlying pathology.

Adult↗
PubMed1998

Pressor and depressor responses in thermocoagulation of the trigeminal ganglion.

We have undertaken a retrospective analysis in 126 patients with trigeminal neuralgia on which a free-hand percutaneous thermocoagulation of the Gasserian ganglion was performed in our department. We focused on the occurrence of intraoperative vagal reactions, i.e. significant bradycardia and changes in blood pressure during the course of the procedure. Operative and anaesthetic records of patients who underwent the procedure were evaluated and correlated with clinical data from the patient's history. We observed the occurrence of vagal reactions i.e. significant bradycardia (< 50/min) or syncope in 20% of patients (p < 0.0002) during or immediately after penetration of the foramen ovale. No correlation between the operated side and the occurrence of vagal reactions was found. A significant rise in blood pressure levels (about 180 mmHg systolic) was observed in 36% of patients during thermocoagulation. We concluded that painful stimuli arising from lesioning in the course of the trigeminal nerve reach the mid-brain and may irritate the dorsal nucleus of the vagus nerve resulting in significant bradycardia or cardiac synode. To prevent haemodynamic deterioration i.v. atropine (0.5-2 mg) should be available when advancing the needle, while anti-hypertensive medication (Esmolol) may be needed during coagulation.

Blood Pressure↗
PubMed1996

Risk analysis of linear accelerator radiosurgery.

PURPOSE: To evaluate the toxicity of stereotactic single-dose irradiation and to compare the own results with already existing risk prediction models. METHODS AND MATERIALS: Computed tomography (CT) or magnetic-resonance (MR) images, and clinical data of 133 consecutive patients treated with linear accelerator radiosurgery were analyzed retrospectively. Using the Cox proportional hazards model the relevance of treatment parameters and dose-volume relationships on the occurrence of radiation-induced tissue changes (edema, localized blood-brain barrier breakdown) were assessed. RESULTS: Sixty-two intraparenchymal lesions (arteriovenous malformation (AVM): 56 patients, meningioma: 6 patients) and 73 skull base tumors were selected for analysis. The median follow-up was 28.1 months (range: 9.0-58.9 months). Radiation-induced tissue changes (32 out of 135, 23.7%) were documented on CT or MR images 3.6-58.7 months after radiosurgery (median time: 17.8 months). The actuarial risk at 2 years for the development of neuroradiological changes was 25.8% for all evaluated patients, 38.4% for intraparenchymal lesions, and 14.6% for skull base tumors. The coefficient: total volume recieving a minimum dose of 10 Gy (VTREAT10) reached statistical significance in a Cox proportional hazards model calculated for all patients, intraparenchymal lesions, and AVMs. In skull base tumors, the volume of normal brain tissue covered by the 10 Gy isodose line (VBRAIN10) was the only significant variable. CONCLUSIONS: These results demonstrate the particular vulnerability of normal brain tissue to single dose irradiation. Optimal conformation of the therapeutic isodose line to the 3D configuration of the target volume may help to reduce side effects.

Adolescent↗