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Biomedical subjects

Karl Kothbauer

Publications and source records attributed to Karl Kothbauer.

4 recordsLinked to original sources
PubMed2004

The refractory period of fast conducting corticospinal tract axons in man and its implications for intraoperative monitoring of motor evoked potentials.

OBJECTIVE: To determine the absolute and relative refractory period (RRP) of fast conducting axons of the corticospinal tract in response to paired high intensity (HI or supramaximal) and moderate intensity (MI or submaximal) electrical stimuli. The importance of the refractory period of fast conducting corticospinal tract axons has to be considered if repetitive transcranial electrical stimulation (TES) is to be effective for eliciting motor evoked potentials (MEPs) intraoperatively. METHODS: Direct (D) waves were recorded from the epidural space of the spinal cord in 14 patients, undergoing surgical correction of spinal deformities. To assess the absolute and RRPs of the corticospinal tract, paired transcranial electrical stimuli at interstimulus intervals (ISI) from 0.7 to 4.1 ms were applied. Recovery of conditioned D wave at short (2 ms) and long (4 ms) ISI was correlated with muscle MEP threshold. The refractory period for peripheral nerve was tested in comparison to that for the corticospinal tract. In four healthy subjects sensory nerve action potentials of the median nerve were studied after stimulation with paired stimuli. RESULTS: HI TES revealed a mean duration of 0.82 ms for the absolute refractory period of the corticospinal tract, while MI stimulation resulted in a mean refractory period duration of 1.47 ms. Stimuli of HI produced faster recovery of D wave amplitude during the RRP. Furthermore, short trains of transcranial electrical stimuli did not elicit MEPs when D wave showed incomplete recovery. A similar influence of stimulus intensity on recovery time was found for the refractory period of peripheral nerve. CONCLUSIONS: The recovery of D wave amplitude is dependent upon stimulus intensity. High intensity produces fast recovery. This is an important factor for the generation of MEPs. When HI TES is used to elicit MEPs, short and long ISIs are equally effective. When MI TES is used to elicit MEPs, only a long ISI of 4 ms is effective.

Action Potentials↗
PubMed2004

Chronic subdural hematoma as a complication of endoscopic third ventriculostomy.

BACKGROUND: Endoscopic third ventriculostomy has become a popular alternative to ventricular shunts for noncommunicating hydrocephalus. Although endoscopic third ventriculostomy is a safe procedure, several complications related to this procedure have been reported in the literature. The authors present a rare case of symptomatic bilateral subdural hematomas after an uneventful endoscopic third ventriculostomy. CASE DESCRIPTION: A 51-year-old male patient presented with symptoms of obstructive hydrocephalus, headaches and memory disturbance. Magnetic resonance imaging demonstrated hydrocephalus secondary to aqueductal stenosis. An endoscopic third ventriculostomy was performed. The patient was discharged home in several days without complication. He then presented with headaches 3 weeks following surgery. A computed tomography study demonstrated bilateral subdural hematomas. These were treated with burr hole evacuation and drainage. Postoperatively, his headaches improved. At last follow-up he remains symptom-free and has radiographic evidence of a patent ventriculostomy. CONCLUSION: This case confirms chronic subdural hematoma formation is a possible complication following third ventriculostomy. Patients should be followed closely for possible subdural hematoma formation.

Hematoma, Subdural, Chronic↗
PubMed2002

Endoscopic third ventriculostomy in patients with cerebrospinal fluid infection and/or hemorrhage.

OBJECT: In this study the authors evaluate the safety, efficacy, and indications for endoscopic third ventriculostomy (ETV) in patients with a history of subarachnoid hemorrhage or intraventricular hemorrhage (IVH) and/or cerebrospinal fluid (CSF) infection. METHODS: The charts of 101 patients from seven international medical centers were retrospectively reviewed; 46 patients had a history of hemorrhage, 42 had a history of CSF infection, and 13 had a history of both disorders. All patients experienced third ventricular hydrocephalus before endoscopy. The success rate for treatment in these three groups was 60.9, 64.3, and 23.1%, respectively. The follow-up period in successfully treated patients ranged from 0.6 to 10 years. Relatively minor complications were observed in 15 patients (14.9%), and there were no deaths. A higher rate of treatment failure was associated with three factors: classification in the combined infection/hemorrhage group, premature birth in the posthemorrhage group, and younger age in the postinfection group. A higher success rate was associated with a history of ventriculoperitoneal (VP) shunt placement before ETV in the posthemorrhage group, even among those who had been born prematurely, who were otherwise more prone to treatment failure. The 13 premature infants who had suffered an IVH and who had undergone VP shunt placement before ETV had a 100% success rate. The procedure was also successful in nine of 10 patients with primary aqueductal stenosis. CONCLUSIONS: Patients with obstructive hydrocephalus and a history of either hemorrhage or infection may be good candidates for ETV, with safety and success rates comparable with those in more general series of patients. Patients who have sustained both hemorrhage and infection are poor candidates for ETV, except in selected cases and as a treatment of last resort. In patients who have previously undergone shunt placement posthemorrhage, ETV is highly successful. It is also highly successful in patients with primary aqueductal stenosis, even in those with a history of hemorrhage or CSF infection.

Adolescent↗