Animal study assessing safety of an acoustic coupling fluid that holds the potential to avoid surgically induced artifacts in 3D ultrasound guided operations.

BACKGROUND: Use of ultrasound in brain tumor surgery is common. The difference in attenuation between brain and isotonic saline may cause artifacts that degrade the ultrasound images, potentially affecting resection grades and safety. Our research group has developed an acoustic coupling fluid that attenuates ultrasound energy like the normal brain. We aimed to test in animals if the newly developed acoustic coupling fluid may have harmful effects. METHODS: Eight rats were included for intraparenchymal injection into the brain, and if no adverse reactions were detected, 6 pigs were to be included with injection of the coupling fluid into the subarachnoid space. Animal behavior, EEG registrations, histopathology and immunohistochemistry were used in assessment. RESULTS: In total, 14 animals were included, 8 rats and 6 pigs. We did not detect any clinical adverse effects, seizure activity on EEG or histopathological signs of tissue damage. CONCLUSION: The novel acoustic coupling fluid intended for brain tumor surgery appears safe in rats and pigs under the tested circumstances.

[Neurophysiological monitoring during surgery]. / Nevrofysiologisk monitorering under kirurgi.

BACKGROUND: Intraoperative neurophysiological monitoring has become increasingly important in interventions involving risk of damage to the nervous system. We aim to provide an overview of possibilities and limitations on the use of intraoperative neurophysiological methods. METHOD: The article is based on a review of relevant textbooks and articles from own literature archives and selective searches in PubMed, combined with the authors' own clinical experience. RESULTS: Intraoperative neurophysiological monitoring includes both continuous monitoring of neural tissue and localisation of vital neurological structures. This monitoring can reduce the risk of damage to nerves and neural pathways and is used most frequently in scoliosis and neurosurgical operations. The need for neurophysiological monitoring influences the choice of anaesthesia, as some anaesthetics affect the monitoring. INTERPRETATION: Intraoperative neurophysiological monitoring is dependent on good cooperation between neurophysiologists, surgeons, anaesthetists and the other specialities involved.

The EEG response to photic stimulation is not increased in alcohol-related seizures.

OBJECTIVE: To investigate the occipital EEG response to 18 and 24Hz photic stimulation (the H-response) in alcohol-related seizures (ARS). METHOD: Twenty-two ARS patients, 15 of whom had a withdrawal seizure (WS) were compared with patients with recent seizures of other causes: 21 patients with epilepsy, and 30 Alcohol Use Disorders Identification Test (AUDIT) negative patients with other seizures. EEG from 37 out-patients with epilepsy and 79 sciatica patents served as patient-controls. The spectral amplitude around 18 and 24Hz and a new photic H-ratio (24/18Hz relative amplitude) was calculated. RESULTS: The H-ratio was significantly reduced in the ARS group compared to the sciatica group. H-ratio reduction correlated with the AUDIT score in ARS patients (p=0.02). No differences between WS and non-WS patients were found for H-response variables. CONCLUSION: A dose-response relationship between AUDIT and the photic response H-ratio was observed in ARS patients. The EEG-driving response to 24Hz flashes was not increased in ARS. SIGNIFICANCE: The relative decrease in 24Hz photic response in ARS reflected drinking severity. The H-ratio is a candidate biomarker for ARS on the group level, although the moderate effect size precludes its use in individual patients.

The impact of extended electrodiagnostic studies in ulnar neuropathy at the elbow.

BACKGROUND: This study aimed to explore the value of extended motor nerve conduction studies in patients with ulnar nerve entrapment at the elbow (UNE) in order to find the most sensitive and least time-consuming method. We wanted to evaluate the utility of examining both the sensory branch from the fifth finger and the dorsal branch of the ulnar nerve. Further we intended to study the clinical symptoms and findings, and a possible correlation between the neurophysiological findings and pain. METHODS: The study was prospective, and 127 UNE patients who were selected consecutively from the list of patients, had a clinical and electrodiagnostic examination. Data from the most symptomatic arm were analysed and compared to the department's reference limits. Student's t - test, chi-square tests and multiple regression models were used. Two-side p-values < 0.05 were considered as significant. RESULTS: Ulnar paresthesias (96%) were more common than pain (60%). Reduced ulnar sensitivity (86%) and muscle strength (48%) were the most common clinical findings. Adding a third stimulation site in the elbow mid-sulcus for motor conduction velocity (MCV) to abductor digiti minimi (ADM) increased the electrodiagnostic sensitivity from 80% to 96%. Additional recording of ulnar MCV to the first dorsal interosseus muscle (FDI) increased the sensitivity from 96% to 98%. The ulnar fifth finger and dorsal branch sensory studies were abnormal in 39% and 30% of patients, respectively. Abnormal electromyography in FDI was found in 49% of the patients. Patients with and without pain had generally similar conduction velocity parameter means. CONCLUSION: We recommend three stimulation sites at the elbow for MCV to ADM. Recording from FDI is not routinely indicated. Sensory studies and electromyography do not contribute much to the sensitivity of the electrodiagnostic evaluation, but they are useful to document axonal degeneration. Most conduction parameters are unrelated to the presence of pain.