Patterns of single-neuron activity during associative recognition memory in the human medial temporal lobe.

Electrophysiological activity in medial temporal lobe (MTL) structures is pivotal for declarative long-term memory. Single-neuron and microcircuit findings capitalizing on human microwire recordings from the medial temporal lobe are still fragmentary. In particular, it is an open question whether identical or different groups of neurons participate in different memory functions. Here, we investigated category-specific responses in the human MTL based on single-neuron recordings in presurgical epilepsy patients performing an associative long-term memory task. Additionally, auditory beat stimuli were presented during encoding and retrieval to modulate memory performance. We describe the proportion of neurons in amygdala, entorhinal cortex, hippocampus and parahippocampal cortex belonging to different response classes. These entail neurons coding stimulus-familiarity, neurons coding successful item memory, and neurons coding associated source memory, as well as the overlap between these classes. As major results we demonstrate that neurons responding to stimulus familiarity (old/new effect) can be identified in the MTL even when using previously known rather than entirely novel stimulus material (words). We observed a significant overlap between familiarity-related neurons and neurons coding item retrieval (remembered/forgotten effect). The largest fraction of familiarity-related neurons was found in the parahippocampal cortex, and a considerable fraction of all parahippocampal neurons was related to successful item retrieval. Neurons related to successful source retrieval were different from the neurons coding the associated information. Most importantly, there was no overlap between neurons coding item memory and those coding associated source memory strongly suggesting that these functions are facilitated by different sets of neurons.

Fractional anisotropy in patients with disproportionately enlarged subarachnoid space hydrocephalus.

BACKGROUND: Disproportionately enlarged subarachnoid space hydrocephalus (DESH) findings on MRI were described as a prognostic factor for responsiveness to the treatment of idiopathic normal pressure hydrocephalus (iNPH). Our premise is that DESH could be associated with compression of the cerebral white matter. Microstructural changes can be identified using diffusion tensor imaging (DTI), specifically fractional anisotropy (FA). The aim of this study is to compare FA in iNPH patients with and without DESH and healthy controls. METHODS: We analysed 1.5-T MRI scans of patients fulfilling the criteria of probable or possible iNPH and positive supplementary tests before and after surgery (ventriculo-peritoneal shunt). FA was measured in the anterior and posterior limb of the internal capsule (PLIC) and in the corpus callosum. Patients were divided into the DESH and non-DESH group. These data were also compared to FA values in the control group. RESULTS: Twenty-seven patients and 24 healthy controls were enrolled. DESH was present in 15 patients and lacking in 12. Twenty-three iNPH patients were shunt responders (85.2 %), and 4 were non-responders (14.8 %). All patients in the DESH group were shunt responders. In the non-DESH group, eight patients were responders (66.7 %). A significant difference between the DESH and non-DESH group was found in the FA of the PLIC. The mean value of FA in the PLIC was 0.72 in the DESH group and 0.66 in the non-DESH group. After the surgery FA decreased in both groups. In the DESH iNPH group FA PLIC decreased to 0.65 and in the non-DESH iNPH group to 0.60. In the healthy controls, the mean FA in the PLIC was 0.58. CONCLUSION: DESH on MRI scans is related to a higher FA in the PLIC with a decrease after the surgery. It reflects a more severe compression of the white matter than in non-DESH patients or healthy volunteers. DESH patients had better outcome than non-DESH patients. This study confirmed the importance of DESH as a supportive sign for iNPH.

Massive pneumorrhachis, pneumocephalus and pneumoopticus following thoracic trauma and avulsion of the brachial plexus: case report and review of the literature.

A 41-year-old man with injury of right half of the thorax, fractures of the left crural bones and paralysis of the right upper limb was admitted to our hospital. A CT examination at admission revealed bilateral pulmonary contusion and bilateral fluid- and pneumothorax. In addition pneumomediastinum, pneumopericardium, subcutaneous emphysema and pneumorrhachis at the cervicothoracic transition was demonstrated. Abnormal findings in the skull and brain were not revealed. The fifth day after admission repeated CT examination demonstrated extensive frontal pneumocephalus on the right, presence of air in several cisterns and in the right optic nerve sheaths (pneumoopticus). Right frontal craniotomy was performed, dura mater was incised and air was evacuated. Rapid regression of pneomocephalus was evident postoperatively. The tenth day after admission MRI of the cervical spine and brachial plexus was performed. At the level of the C7 and C8, nerve roots pneumomenigocele and a nerve retracting ball indicating the presence of a nerve root injury were discernible. This case demonstrated that severe thoracic blunt trauma leads to acute increase of intrathoracic pressure with concomitant fluid- and pneumothorax, pneumomediastinum and pneumopericard. From the mediastinum air propagated subcutaneously. Disrupted cervical dural sheaths resulted in leakage of cerebrospinal fluid and entry of air from mediastinum to subdural and subarachnoid spinal and cranial space and to the subarachnoid space of the optic nerve.

[Myocardial ischaemia resulting from compression of coronary artery caused by herniation of abdominal organs into thoracic cavity]. / Myokardiální ischémie vzniklá útlakem vencité tepny herniovanými orgány dutiny brisní do hrudní dutiny.

A case of 40-year-old patient with compression of coronary artery and myocardial ischaemia is presented. Compression resulted from the herniation of abdominal organs into the thoracic cavity, which developed many years after the car accident trauma.