Biological Basis of Behavior
Mohamed Ahmed Abd El-Hay in Understanding Psychology for Medicine and Nursing, 2019
Only primates have temporal lobes, which are largest in man, accommodating about 25 percent of the cerebral cortex and including areas with auditory, olfactory, vestibular, visual, and linguistic functions. Important regions of the temporal lobe include Heschl’s gyrus (primary auditory cortex) and the auditory association cortex, which includes the planum temporale in the temporal operculum, the superior, middle, and inferior temporal gyri, and the occipitotemporal (fusiform) gyrus. On the inferiomedial surface of the temporal lobe lies the parahippocampal gyrus, which contains the hippocampal formation. On the medial aspect of the anterior portion of the parahippocampal gyrus is the uncus, a small bulge on the surface of the brain that marks the general location of the amygdala lying beneath this surface feature. The temporal lobes are associated with the processing of auditory input and with the encoding of memory. The temporal lobes also may play a substantial role in the processing of affective information, language, and in certain aspects of visual perception. The left side of the temporal lobe deals with language and verbal memory, while the right side deals with the ability to process non-verbal sounds and non-verbal memory (Mendoza & Foundas, 2007).
Neurology cases
Lt Col Edward Sellon, David C Howlett, Nick Taylor in Radiology for Medical Finals, 2017
Figure 9.6B shows the ‘mass effect' from the right frontal haematoma with a clear midline shift. There is displacement of the anterior horns of the lateral ventricles to the left and the frontal horn of the right lateral ventricle is partly effaced (Figure 9.6D).The haematoma displaces the entire right cerebral hemisphere. The cranium is essentially a closed box (see the Monro–Kellie hypothesis), and the extra volume caused by the haematoma inevitably effaces the CSF spaces (sulci, ventricles) and displaces structures, initially across the midline (subfalcine herniation).As intracranial pressure increases further, the brain is pushed inferiorly through the tentorium cerebelli (tentorial herniation). The uncus may also be displaced inferiorly (uncal herniation).Uncal herniation is typically a preterminal event as vital brainstem function is compromised.
The management of major injuries
Ashley W. Blom, David Warwick, Michael R. Whitehouse in Apley and Solomon’s System of Orthopaedics and Trauma, 2017
As the pressure rises, the conscious level decreases and the GCS falls. The medial part of the temporal lobe (the uncus) herniates through the tentorial notch, compressing the third cranial nerve and the midbrain pyramidal tracts. This usually results in pupillary dilatation on the side of the injury, and hemiplegia on the opposite side. Pressure changes in the medulla cause a sympathetic discharge, with a rise in blood pressure and reflex bradycardia. With further pressure rise, cerebral blood flow is compromised, and it ceases terminally when the ICP rises above the mean arterial pressure (MAP). Ultimately, the cerebellar tonsil is forced into the foramen magnum, resulting in a loss of vital cardiorespiratory function; this is known as brainstem or brain death, and it is a terminal event.
Investigational drugs for the treatment of olfactory dysfunction
Published in Expert Opinion on Investigational Drugs, 2022
Arianna Di Stadio, Cinzia Severini, Andrea Colizza, Marco De Vincentiis, Ignazio La Mantia
The neuroepithelium is connected through the axons of the ORN to the olfactory bulb, which contains glomerulus, mitral cells and tufted relay neurons. The axons converge in the glomerulus to form the first cranial nerve (olfactory nerve). The glomerulus is connected by synapses to the mitral cells; the latter together with the tufted relay neurons forms the olfactory tract. This structure bifurcates in the medial and lateral olfactory stria (y inverted-shaped). The olfactory stimulus is conducted through these structures up to the piriform cortex, the periamygdaloid cortex, the olfactory tuberculosis and the anterior olfactory nucleus. The primary olfactory cortex is formed by the medial and lateral olfactory stria and the anterior perforated substance. The lateral olfactory stria is extended posteriorly giving origin to the entorhinal area which, together with the uncus, forms the secondary olfactory cortex, also known as the orbitofrontal cortex (Figure 2). This area is straightly related to memory. The primary cortex is responsible for the active perception of the sense of smell, while the secondary one is the portion where the smell perception is integrated with emotions and memory.
Chameleons, red herrings, and false localizing signs in neurocritical care
Published in British Journal of Neurosurgery, 2022
Boyi Li, Tolga Sursal, Christian Bowers, Chad Cole, Chirag Gandhi, Meic Schmidt, Stephan Mayer, Fawaz Al-Mufti
The classical pathophysiology of KWNP is compression of the contralateral cerebral peduncle above the medullary decussation against the free border of the tentorium, caused by a mass lesion inducing herniation of the uncus.59 The pathophysiology of the less common clinical presentations are likely derived from anatomic proximity of structures such as cranial nerves, hippocampus, posterior cerebellar and superior cerebellar arteries, which can all be affected by such herniations.59 When KNWP is suspected in the presence of ipsilateral hemiparesis, CT can identify the cause and herniation, but typically do not yield as much information as MRI.59,60 Neurophysiological studies have shown that somatosensory evoked potentials and transcranial magnetic stimulation help in characterizing KNWP; however, further research is required.59
Absence of CSF flow within the cerebral aqueduct in spontaneous intracranial hypotension: a report of two cases
Published in British Journal of Neurosurgery, 2021
Ferhat Yıldırım, Aynur Turan, Selda Güven, Tuba Akdağ
The MRI findings of SIH are pachymeningeal enhancement, sagging of the brain structures, pituitary hyperaemia, subdural fluid collections, and distension of venous structures. Additionally, the bilateral downward displacement of the uncus can be seen, as in our first patient.7 Although limited in the literature, CSF flow analysis with various MRI techniques can also be performed to contribute to SIH diagnosis.9 In this way, CSF flow can be evaluated qualitatively and quantitatively with these techniques. The most commonly used PC-MRI technique generates the signal from the phase shift between flowing and stationary protons. This phase shift is generated using Venc gradients proportional to the velocity of moving protons. This phenomenon demonstrates the velocity sensitivity of gradients and is defined by the user before image acquisition to measure the velocity of protons. The cerebral aqueduct is anatomically open in a normal population, and typical CSF flow and mean Venc values are 5–8 cm/s. Low Venc values (2–4 cm/s) are used to evaluate ventriculoperitoneal shunt patency and differentiate between communicated and non-communicated arachnoid cysts. Higher Venc values (20–25 cm/s) are chosen to detect hyperdynamic CSF circulation such as normal pressure hydrocephalus.3
Related Knowledge Centers
- Brain Herniation
- Dentate Gyrus
- Morphology
- Olfactory System
- Parahippocampal Gyrus
- Neoplasm
- Temporal Lobe
- Rhinal Sulcus
- Rhinencephalon
- Seizure