Intraparenchymal and interventricular hemorrhage
Definition
Intraparenchymal hemorrhage (IPH), aka, intercerebral hemorrhage, is a bleed that occurs within the brain parenchyma or the functional tissue in the brain consisting of neurons and glial cells. A hemorrhage, or the profuse release of blood from a ruptured blood vessel in the brain, disrupts normal blood flow and subsequently deprives the brain of oxygen. As a result, the brain cells can die, which damages the affected nerves and the related functions they control as well. Spontaneous IPH accounts for less than 20% of stroke cases, but it is associated with the highest mortality rates of all forms of stroke. IPH can be classified as primary or secondary, depending on the cause. Primary IPH accounts for about 80% of cases, occurring when there is a spontaneous rupture of damaged arteries. Meanwhile, secondary IPH is due to an underlying condition that increases the likelihood of hemorrhage. The bleed seen here probably diffused into the ventricles causing the Interventricular hemorrhage.
Radiology
Intraparenchymal hemorrhage is a subset of an intracranial hemorrhage and encompasses a number of entities that have in common the acute accumulation of blood within the parenchyma of the brain. The etiology, epidemiology, treatment, and prognosis vary widely depending on the type of hemorrhage, and as such, these are discussed separately.
They are most often broadly divided according to whether they are spontaneous (primary) or due to an underlying lesion (secondary), and then further divided according to etiology and/or location.
Anatomical Correlations and Exercises
Identify the following brain structures using the available specimens. See the frontal lobe, temporal lobe, parietal lobe, and occipital lobe. By spreading apart the parietal lobes manually along the longitudinal fissure, the corpus callosum can be seen running between the two lobes.
Click here to see the lateral aspect of the brain.
Click here to see the ventricular system of the brain.
The cerebellum overlies the posterior aspect of the pons and medulla and extends laterally beneath the tentorium cerebelli (see below, Dura). The cerebellum is mainly concerned with motor functions that regulate posture, muscle tone, and muscular coordination.
The external aspect of the cerebrum is characterized by a series of fissures and sulci. These include the longitudinal cerebral fissure which contains the falx cerebri, a sagittally placed septum of dura between cerebral lobes. This fissure extends inferiorly (deep) only as far as the corpus callosum which is a composite of decussating nerve fibers crossing between cerebral hemispheres. See here.
The transverse cerebral fissure separates the cerebral hemispheres from the cerebellum and contains the horizontal slip of dura called tentorium cerebelli. The lateral sulcus separates the frontal and temporal lobes. The central sulcus is a prominent groove in the central portion of the cerebral hemispheres. It is an important landmark since it separates the motor cortex (precentral gyrus) from the general sensory cortex (postcentral gyrus). The parietooccipital sulcus separates parietal and occipital lobes. The calcarine sulcus is seen from the sagittal (medial) aspect and it commences near the occipital pole and runs anteriorly eventually joining the parietooccipital sulcus. Identify as many of these structures as possible.
Interventricular shift
Definition
An interventricular shift can occur when a lesion, tumor, hemorrhage, or abscess exerts a mass effect on the brain parenchyma and cause lateral shift of the midline structures. One of the most important indicators of increased intracranial pressure is the presence of a midline shift of the ventricles.
Radiology
Midline shift is measured in millimeters, as the perpendicular distance between a midline structure, typically the septum pellucidum, and a line designated the midline. The midline is assumed to be coplanar with the falx cerebri, and is best represented as a line drawn between the anterior and posterior attachments of the falx to the inner table of the skull. Care must be taken if there is an existing asymmetry of the ventricles or the falx.
Anatomical Correlations and Exercises
Review the falx, ventricles, and midline brain structures on the split-brain specimens.