Perimesencephalic subarachnoid hemorrhage with a positive angiographic finding: case report and review of the literature.

The vast majority of perimesencephalic subarachnoid hemorrhage cases are reported as negative-finding etiologies. Recently, high-resolution images allowed us to overcome the previous difficulty of finding the source of bleeding, which underlies the concept of a "negative finding". We discovered a venous etiology, hidden behind the tip of the basilar artery; namely, the lateral pontine vein. Here, we review the literature on perimesencephalic subarachnoid hemorrhage and on venous aneurysm. We highlight this type of aneurysm as a candidate source of perimesencephalic hemorrhage. This case may change our way of dealing with what we have termed a negative finding of subarachnoid hemorrhage.

Association of admission plasma glucose level and cerebral computed tomographic perfusion deficit volumes.

INTRODUCTION: Hyperglycemia in acute ischemic stroke (AIS) is frequent and associated with worse outcome. Yet, strict glycemic control in AIS patients has failed to yield beneficial outcome. So far, the underlying pathophysiological mechanisms of admission hyperglycemia in AIS have remained not fully understood. We aimed to evaluate the yet equivocal association of hyperglycemia with computed tomographic perfusion (CTP) deficit volumes. PATIENTS AND METHODS: We included 832 consecutive AIS and transient ischemic attack (TIA) patients who underwent CTP as a part of screening for recanalization treatment (stroke code) between 3/2018 and 10/2020, from the prospective cohort of Helsinki Stroke Quality Registry. Associations of admission glucose level (AGL) and CTP deficit volumes, namely ischemic core, defined as relative cerebral blood flow <30%, and hypoperfusion lesions Time-to-maximum (Tmax) >6 s and Tmax >10s, as determined with RAPID® software, were analyzed with a linear regression model adjusted for age, sex, C-reactive protein, and time from symptom onset to imaging. RESULTS: AGL median was 6.8 mmol/L (interquartile range 5.9-8.0 mmol/L), and 222 (27%) patients were hyperglycemic (glucose >7.8 mmol/L) on admission. In non-diabetic patients (643 [77%]), AGL was significantly associated with volume of Tmax. >6 s (regression coefficient [RC] 4.8, 95% confidence interval [CI] 0.49-9.1), of Tmax >10s (RC 4.6, 95% CI 1.2-8.1), and of ischemic core (RC 2.6, 95% CI 0.64-4.6). No significant associations were shown in diabetic patients. CONCLUSION: Admission hyperglycemia appears to be associated with both larger volume of hypoperfusion lesions and of ischemic core in non-diabetic stroke code patients with AIS and TIA.

Comparative analysis of core and perfusion lesion volumes between commercially available computed tomography perfusion software.

Introduction: Computed tomography perfusion (CTP) imaging has become an important tool in evaluating acute recanalization treatment candidates. Large clinical trials have successfully used RAPID automated imaging analysis software for quantifying ischemic core and penumbra, yet other commercially available software vendors are also on the market. We evaluated the possible difference in ischemic core and perfusion lesion volumes and the agreement rate of target mismatch between OLEA, MIStar, and Syngo.Via versus RAPID software in acute recanalization treatment candidates. Patients and methods: All consecutive stroke-code patients with baseline CTP RAPID imaging at Helsinki University Hospital during 8/2018-9/2021 were included. Ischemic core was defined as cerebral blood flow <30% than the contralateral hemisphere and within the area of delay time (DT) >3s with MIStar. Perfusion lesion volume was defined as DT > 3 s (MIStar) and Tmax > 6 s with all other software. A perfusion mismatch ratio of ⩾1.8, a perfusion lesion volume of ⩾15 mL, and ischemic core <70 mL was defined as target mismatch. The mean pairwise differences of the core and perfusion lesion volumes between software were calculated using the Bland-Altman method and the agreement of target mismatch between software using the Pearson correlation. Results: A total of 1606 patients had RAPID perfusion maps, 1222 of which had MIStar, 596 patients had OLEA, and 349 patients had Syngo.Via perfusion maps available. Each software was compared with simultaneously analyzed RAPID software. MIStar showed the smallest core difference compared with RAPID (-2 mL, confidence interval (CI) from -26 to 22), followed by OLEA (2 mL, CI from -33 to 38). Perfusion lesion volume differed least with MIStar (4 mL, CI from -62 to 71) in comparison with RAPID, followed by Syngo.Via (6 mL, CI from -94 to 106). MIStar had the best agreement rate with target mismatch of RAPID followed by OLEA and Syngo.Via. Discussion and conclusion: Comparison of RAPID with three other automated imaging analysis software showed variance in ischemic core and perfusion lesion volumes and in target mismatch.

De novo giant A2 aneurysm following anterior communicating artery occlusion.

BACKGROUND: De novo intracranial aneurysms are reported to occur with varying incidence after intracranial aneurysm treatment. They are purported to be observed, however, with increased incidence after Hunterian ligation; particularly in cases of carotid artery occlusion for giant or complex aneurysms deemed unclippable. CASE DESCRIPTION: We report a case of right-sided de novo giant A2 aneurysm 6 years after an anterior communicating artery (ACoA) aneurysm clipping. We believe this de novo aneurysm developed in part due to patient-specific risk factors but also a significant change in cerebral hemodynamics. The ACoA became occluded after surgery that likely altered the cerebral hemodynamics and contributed to the de novo aneurysm. We believe this to be the first reported case of a giant de novo aneurysm in this location. Following parent vessel occlusion (mostly of the carotid artery), there are no reports of any de novo aneurysms in the pericallosal arteries let alone a giant one. The patient had a dominant right A1 and the sudden increase in A2 blood flow likely resulted in increased wall shear stress, particularly in the medial wall of the A2 where the aneurysm occurred 2 mm distal to the A1-2 junction. CONCLUSION: ACoA preservation is a key element of aneurysm surgery in this location. Suspected occlusion of this vessel may warrant closer radiographic follow-up in patients with other risk factors for aneurysm development.

The motor cortex approximately 20 Hz rhythm reacts differently to thumb and middle finger stimulation: an MEG study.

The human thumb is functionally and morphologically different from the other digits, enabling capability for a wide range of movements and for precision grasping. We investigated the reactivity of the magnetic approximately 20 Hz motor cortex rhythm by stimulating thumb and middle finger electrically and by quantifying the poststimulus rebounds. The level of the approximately 20 Hz rhythm level was significantly higher after thumb than middle finger stimulation. In contrast, the somatosensory 20-ms responses were stronger after middle finger than the thumb stimulation. We found an inverse thumb/middle finger ratio between the 20 ms responses and the reactivity of the approximately 20 Hz motor cortex rhythm. Thus the sensorimotor processing differs for thumb and middle finger in the human primary motor and somatosensory cortices.

Manifest disease and motor cortex reactivity in twins discordant for schizophrenia.

Schizophrenia is often associated with difficulties in distinguishing between actions of self and of others. This could reflect dysfunction of the mirror neuron system which directly matches observed and executed actions. We studied 11 people with schizophrenia and their co-twins without manifest disease, using stimulus-induced changes in the magnetoencephalographic approximately 20 Hz rhythm as an index of activation in the motor cortex part of the mirror neuron system. During action observation and execution, motor cortex reaction was weaker in those with schizophrenia than in their co-twins, suggesting a disease-related dysfunction of motor cognition.

Viewing speech modulates activity in the left SI mouth cortex.

The ability to internally simulate other persons' actions is important for social interaction. In monkeys, neurons in the premotor cortex are activated both when the monkey performs mouth or hand actions and when it views or listens to actions made by others. Neuronal circuits with similar "mirror-neuron" properties probably exist in the human Broca's area and primary motor cortex. Viewing other person's hand actions also modulates activity in the primary somatosensory cortex SI, suggesting that the SI cortex is related to the human mirror-neuron system. To study the selectivity of the SI activation during action viewing, we stimulated the lower lip (with tactile pulses) and the median nerves (with electric pulses) in eight subjects to activate their SI mouth and hand cortices while the subjects either rested, listened to other person's speech, viewed her articulatory gestures, or executed mouth movements. The 55-ms SI responses to lip stimuli were enhanced by 16% (P<0.01) in the left hemisphere during speech viewing whereas listening to speech did not modulate these responses. The 35-ms responses to median-nerve stimulation remained stable during speech viewing and listening. Own mouth movements suppressed responses to lip stimuli bilaterally by 74% (P<0.001), without any effect on responses to median-nerve stimuli. Our findings show that viewing another person's articulatory gestures activates the left SI cortex in a somatotopic manner. The results provide further evidence for the view that SI is involved in "mirroring" of other persons' actions.

Activation of the human primary motor cortex during observation of tool use.

Tool use is a characteristic human trait, requiring motor skills that are largely learned by imitation. A neural system that supports imitation and action understanding by directly matching observed actions and their motor counterparts has been found in the human premotor and motor cortices. To test whether this "mirror-neuron system" (MNS) would be activated by observation of tool use, we recorded neuromagnetic oscillatory activity from the primary motor cortex of 10 healthy subjects while they observed the experimenter to use chopsticks in a goal-directed and non-goal-directed manner. The left and right median nerves were stimulated alternatingly, and the poststimulus rebounds of the approximately 20-Hz motor-cortex rhythms were quantified. Compared with the rest condition, the level of the approximately 20-Hz rhythm was suppressed during observation of both types of tool use, indicating activation of the primary motor cortex. The suppression was on average 15-17% stronger during observation of goal-directed than non-goal-directed tool use, and this difference correlated positively with the frequency of subjects' chopstick use during the last year. These results support the view that the motor-cortex activation is related to the observer's ability to understand and imitate motor acts.