Therapeutic application of 20-kHz transcranial ultrasound in an embolic middle cerebral artery occlusion model in rats: safety concerns.

BACKGROUND AND PURPOSE: Therapeutic application of diagnostic ultrasound has been shown to improve recanalization rates in patients with acute cerebral vessel occlusion. There is experimental evidence that low-frequency ultrasound may be superior. This study was designed to evaluate the therapeutic efficacy and safety of low-frequency ultrasound in an embolic middle cerebral artery occlusion model in rats. A parameter setting was used that had not previously shown any side effects and interactions with healthy rat brain tissue. METHODS: Male Wistar rats were submitted to middle cerebral artery clot embolism and transcranial treatment with 20-kHz continuous-wave ultrasound (0.2 W/cm(2)), either alone or in combination with recombinant tissue-type plasminogen activator. Control groups received no treatment or recombinant tissue-type plasminogen activator alone. Outcome assessment consisted of determination of infarct volume and neurological evaluation. RESULTS: Eleven animals treated with ultrasound died during the follow-up period of 7 days, compared with 2 animals in the control groups (P=0.028). In 3 animals, subarachnoid hemorrhage was detected (1 in the control group). The other animals that died displayed secondary worsening after an initial period of normal vigilance. Histological examination revealed massive edema formation. In surviving animals, no benefit of treatment could be demonstrated. CONCLUSIONS: In this study, 20-kHz continuous-wave ultrasound caused death in a significant number of animals. Ultrasound at 20 kHz does not seem to be suitable for transcranial therapeutic cerebral application. The data underline the necessity to obtain further animal data to establish the safety limits of frequency and power output.

Cerebral embolic ischemia in rats: correlation of stroke severity and functional deficit as important outcome parameter.

The embolic MCA occlusion model in rats is used for recanalisation studies in acute stroke. In addition to the determination of lesion size, the assessment of functional outcome may improve the value of this model. Male Wistar rats were submitted to MCA clot embolism or sham surgery. In order to achieve a larger variety of lesion volume, 2 subgroups (each 7 animals) were subjected to differently sized emboli (30 and 40 mm). Follow-up period was 6 days. Outcome assessment consisted of a test battery including parallel bar crossing, observation of behaviour in an open field and an 8-arm maze and a neurological score with ten different sensorimotor and coordinative items. Animals were perfusion-fixed on day 7 (blinded examination). For both subgroups, there were significant impairments with regard to performance on the Neuro score, parallel bar crossing and maze exploration. Improvement was only partial during the follow-up period. On follow-up day 6, there was still a significant correlation between total infarct volume and functional outcome on the Neuro score (R=0.80, p=0.0006) and the exploration behaviour in the maze (R=0.66, p=0.01). Application of emboli with a length of 40 mm caused more functional impairment and a more extended lesion volume compared with 30 mm. We present outcome tests that provide quantitative and objective tools to test functional impairment in rats following embolic stroke.

Early diagnosis of Acanthamoeba infection during routine cytological examination of cerebrospinal fluid.

Early identification of Acanthamoeba in cerebrospinal fluid is mandatory to prevent fatal granulomatous amebic encephalitis. In the case presented here amebic trophozoites were detected in a routine cerebrospinal fluid sample. The antibiotic treatment and the apparently low virulence of this isolate were responsible for the benign progression of the infection.