Character | Brain

Ashley Davidoff MD

Introduction

Character refers to the look and feel of the structure. The character of the brain is not easily defined but it is best described as a gelatinous wrinkled inelastic mass with a light creamy color, that feels like jello or like soft butter.

The surface of the hemispheres is all cortical matter and is pinkish-beige in color and slightly off-white in the interior. Its consistency is comparable to soft gelatin. About 77% of the brain is made up of water, 10-12% being fat. It has 6 cortical layers.

The distinction between gray and white matter is easily made due to the lighter color of the white matter and the more pinkish color of the cortex. The ventricular system at the dissection table is devoid of its clear water like CSF and appears as an empty space in the mddle of the brain and contains the soft tissue components of the choroid plexus most voluminous posteriorly.

Creamy Color and “Jello-Like” to the Feel

The brain has a characteristic appearance manifest by its creamy color, characteristic shape and fissured surface. To the feel it is said to feel like soft butter.

The anatomic specimen reveals an external view of the brain. The characteristic cream color of the brain can be appreciated on this specimen. This reflects the color of the gray matter and external portion of the cortex

The surface of the hemispheres is known as cortex. It presents as a system of irregular prominences (called convolutions or gyri) that circumscribe depressions (called fissures or sulci) which are somewhat profound and full of twists and turns.

The sulci and gyri of the forebrain are distinctly different from the pattern of the cerebellum.

The relative size of the forebrain compared to the hindbrain is also well demonstrated

Courtesy of Thomas W.Smith, MD; Department of Pathology, University of Massachusetts Medical School. 97804

Miodsagittal View

The midsagittal section view of brain reveals the distinction between the character of the cerebral cortex which has a creamy color and the white matter exemplified by the corpus callosum (cc white), and the midbrain (mb), pons (p) and medulla (m) which are off white in color as opposed to the color of the cerebellum (c) which is light salmon pink in color.

The relative sizes of the forebrain, midbrain and hindbrain are also well appreciated in this section.

Image Courtesy of Thomas W.Smith, MD; Department of Pathology, University of Massachusetts Medical School. 97805b01

The basal ganglia and other conglomerates of nuclii appear with the same color to great extent as the cortex, ie slightly darker than the white matter

Acute Hemorrhagic Infarction

The brain has a characteristic appearance characterised by its creamy color and characteristic shape and fissured surface. This pathological specimen shows an acute hemorrhagic infarct in the left frontoparietal region with necrosis of the brain tissue and mass effect on the lateral ventricle and midline shift. The specimen also serves to reveal the normal right side with its creamy color and darker brownish gray matter that is accentuated by increasing the contrast on the right image (b). Other structures that are seen include the corpus callosum that lies above the ventricles (cc), the caudate nucleus (c) that lies inferior to the lateral ventricle, the line of white matter between the caudate and putamen called the internal capsule, the 3rd ventricle (3) medial to these structures , and the thalamus (th) inferior to them. The interhemispheric fissure (if) is seen superiorly and the Sylvian fissure (Sf) is seen laterally. The horizontal folds and darker color of the cerebellum are characteristics of that structure.

Character of the Brain by MRI

Its character is best exposed in vivo by its MRI characteristics, and even better under the microscope with specific stains.

MRI with multiple available sequence is the best in vivo way to evalaute the structural character of the brain and PET scanning the best way to examine the functional characyer of the brain.

T2 weighted images are very sentive to water and therefor reveal the nature of the vebtricles and by outlining the sulci theyreflect the anatomy of the gyri. They are also very usefil in defining the form of the cisterns.

T1 Weighted Sagittal Image Normal Brain

The T1 weighted images have good spatial resolution but inferior contrast resolution meaning in the latter instance that the images are more gray when compared to more black and white contrats of T2 weighted images.

Fat though is quite bright as seen in the subcutaneous tissues and to lesser extent in the bone marrow. Air in the maxillary sinus is quite black while the CSF is a dull charcoal. White matter like the corpus callosum are well seen and the midbrain hind brain, and spinal cord are quite well seen.

49079b01 brain cerebrum cerebral normal anatomy MRI T1 weighted sagital Davidoff MD

T2 Weighted Axial Image Through the Middle of the Lateral Ventricles

This axial image of a normal T2 weighted MRI scan shows high intensity CSF anatomy. Note the presence of the lower signal intensity of the choroid plexus in the occipital horms and the excquisite definirtion of the thin sulci and hence the gyral pattern.

In this instance the T2 characteristics of the the caudate nuclii that lie just lateral and posterior to the frontal horns are very similar to the putamen which also retains slight hyperintensity with tiny punctate ares of T2 hyperintensity.

The corpus callosum on the other hand including the “V” shaped genu between the frontal horns, and the inverted V shaped splenium between the posterior occipital horns are composed of white matter and contain little water and are therefore quite dark on the T2 weighted images.

Courtesy Ashley Davidoff MD 38703c03g code CNS brain CSF normal

Character of the Brain by CT Scan

Normal Head CT

Distinction Between Gray and White Matter

The two images are form the same patient and the routine settings are shown on the left and the windows have been further narrowed on the right image in order to accentuate the difference between the gray and white matter. CT shows the white matter to be darker (blacker) than the gray matter which is a thin mantle of tissue on the edge of the brain. The ability to distinguish gray matter from white matter is a far easier task on MRI.

Normal – 4 months Prior and Folllowing Cardiopulmonary Arrest

Loss of Gray White Differentiation

The CT is from a 52 year old female who had a CT 4 months prior tto a cardiac arrest (a) showing subtle but definite difference in the attenuation difference between gray and white matter.

After the cardiac arrest, she suffered anoxic injury to the brain resulting in extensive and global swelling of the brain and both gray and white matter have the same attenuation. The distinction between the two cannot be made and this finding is consistent with global anoxic injury.

After 10-15 seconds of anoxia from cardiac arrest, loss of conciousness occurs and after 5 minutes of arrest, irreversible brain injury occurs.

The gray matter of the brain, particularly the frontal lobes have highest metabolic needs. The occipital, parietal, and temporal lobes and basal ganglia and cerebellum have lesser needs. The brainstem has the lowest oxygen needs

Ultrasound Characteristics of the Neonatal Brain

The ultrasound of a 7 day old baby boy reveals a normal sagittal section through the brain showing the CSF filled lateral ventricle (light blue) with most the brain substance showing characteristic homogeneous solid organ texture. The echogenic interfaces of the sulci with the gyri enable the outline of characteristic forms of the gyri so that for example the cingulate gyrus (darker green) is easily recognized by its classical location above the corpus callosum (purple). The corpus callosum is hypoechoic and overlaid in purple. The thalamus is isoechoic (orange) recognized by its position and shape rather than any unique ultrasound characteristics. The forebrain including the frontal parietal and temporal lobes are overlaid in green brain

Disease States

Character of Acute Hemorrhage

Acute Thalamic Hemorrhage

The CT is from a 77year old male with acute neurological deficit The epicenter of the disease is an acute hemorrhage in the right thalamus, bright red in (b,d) with extension of the clot into the ventricle (maroon). There is non clotted blood lying dependently in the occipital horns (dense on c) presenting as a CSF-blood level (light pink on black CSF) in (d). The hemorrhage is surrounded by a rim of edema (light yellow) as seen in b and d.

Hyperacute Hemorrhage in the Right Thalamus

The MRI is from a 77year old male with acute neurological deficit The epicenter of the disease is a hemorrhage in the right thalamus. The T1 weighted image (upper left) shows mostly hypointense signal indicating the presence of deoxyhemoglobin. On the T2 weighted image the signal of the hematoma is also mostly hypointense confirming the hyperacute nature of the hematoma, surrounded by a ring of increased signal reflecting edema. There is a layering effect of blood in the posterior horn on the left The presence of deoxyhemoglobin dates the hemorrhage between minutes to hours The FLAIR image (c) shows the hyperacute hematoma as hypointense and the surrounding edema as hyperintense. The GRE image fails to reveal hemosiderin deposit in the periphery making chronic hemorrhage unlikely. The diagnosis of hyperacute intracerebral hemorrhage (minutes to hours) is therefore made by the presence of deoxyhemoglobin hypo/isointensity on the T1 weighted images and the hypointensity on T2 weighted. The suurounding edema is best seen on the T2 and FLAIR images. The extension into the ventricles is apparent on all sequences.

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