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Neuroanatomy Video Lab: Brain Dissections

The Spencer S. Eccles Health Sciences Library at the University of Utah and Suzanne Stensaas, PhD present Neuroanatomy Video Lab: Brain Dissections.

 Overview of Series of Neuroanatomy Video Dissections and Lessons

This series of Neuroanatomy “lessons” has two principal objectives. The first is to provide viewers access to human brain specimens, something lacking in many places. The second is to simplify the anatomy, omitting many details, and making many generalizations.  The reason for this is to keep the focus on localization of the patient’s disease within the nervous system. Students are often overwhelmed with excessive detail making correlation of structure and function more difficult. The presentation sequence is in a logical order for a class, but each video is designed to standalone and be used just-in-time to make a clinical point.

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The series originated when teaching with a neurologist in Ghana and Kenya where it was clear that anatomy taught separated from the clinic by many years was not retained. Here I present just enough anatomy to localize the patient’s problem. These videos can be used before or after a clinical case presentation. Apologies are offered for a few minor errors that could not be corrected due to the one time recording opportunity as well as an unscripted personal style. The audience for these videos can be nurses, physician assistants, medical students, residents, registrars, house officers or anyone interested in the brain. Videos can also be used in conjunction with the NeurologicExam Website, http://library.med.utah.edu/neurologicexam/html/home_exam.html All of the videos have English captions to assist those for whom English is not their native language or to visualize the many new terms. Videos can be downloaded at http://library.med.utah.edu/neurologicexam/html/brain-dissections.html for those lacking bandwidth or Internet connectivity. They may be shared, copied, distributed and put on local servers. I am indebted to the Eccles Health Sciences Library of the School of Medicine for the videography and server support and to Paul Burrows from Teaching and Learning Technology at the University of Utah for creating and maintaining the NeuroLogic Exam website. Finally I acknowledge neurologists Dr. David Renner and Dr. Leonard Jarcho who showed me the anatomy that was most important in their practice of medicine. Suzanne S. Stensaas, Ph.D., Professor Emeritus Department of Neurobiology and Anatomy School of Medicine, University of Utah
Video Playlist
01 – Introduction (14 minutes) The regions and lobes of the brain are identified along with some of the nerves and vessels. The basic functions of the cortex of each lobe are introduced along with principal sulci and gyri. The importance of the left hemisphere for language and the temporal lobe in memory are mentioned along with the concept of cortical localization. A classical frontal section is used to demonstrate gray and white matter along with the primary internal structures.

 

02 – The Normal Unfixed Brain (6 minutes) The consistency and vulnerability of the brain is demonstrated along with the clear and glistening pia and arachnoid and the tough dura. The cushioning function of the CSF is stressed and the features are pointed out on the ventral surface. The uncus and temporal lobes are normal with arteries free of atherosclerosis.

 

03 – Orientation: The Planes of the Brain (8 minutes) Terms such as anterior, posterior, inferior and superior are introduced with respect to the hemispheres as well as the brain stem. Terms such as rostral and caudal or dorsal and ventral can mean different things in different areas. Sections in three planes (frontal, axial, and sagittal) are demonstrated on gross specimens along with key features including the ventricular system.

 

04 – The Meninges (15 minutes) The epidural, subdural and subarachnoid spaces are demonstrated and discussed with respect to trauma and disease. The relationship of the brainstem and cerebellum to the tentorium demonstrates the vulnerability of the brain stem to increased supratentorial pressure and herniation. Arachnoid granulations and the sagittal sinus are shown. A subdural hematoma specimen as well as sections from a ruptured aneurysm complete the demonstration.

 

05 – The Ventricles (27 minutes) The ventricles are demonstrated and named on a model cast as well as in rotating 3D reconstructions. The production, function, circulation and removal of CSF produced by the choroid plexus is discussed using a diagram and then reviewed on frontal, axial and sagittal brain specimens and corresponding MRI’s. The blood CSF and brain barriers are mentioned along with the cisterns.

 

06 – The Spinal Cord and Monosynaptic Reflex (17 minutes) The spinal cord’s relationship to the foramina, discs and spinal nerves is demonstrated on a model. The dura, ganglia and rootlets are shown as well as the gray and white matter in gross sections at different levels. A model of the cord is used to demonstrate and describe the anatomy of a monosynaptic reflex and the concept of a dermatome. Finally, a myelin stained cord section is described and related to the gross demonstration.

 

07 – The Unfixed Spinal Cord (7 minutes) The delicate and soft cord partially covered with dura is seen with the anterior and posterior spinal arteries and a description of the structures they supply. The dural sac is opened showing the dorsal and ventral roots in the cauda equina.

 

08 – Cranial Nerves (12 minutes) The approach is to learn to associate the cranial nerves with their brainstem level and blood supply. Emphasis is given to the midbrain (3, 4), pons (5, 6, 7, 8), medulla (9, 10, 11, 12) and their most important functions.

 

09 – Brain Stem & Reflexes (25 minutes) The cranial nerves are reviewed again on a specimen with vessels. Next, landmarks on gross brain stem sections are shown. Stressed are the three reflexes associated with each of the three levels: pupillary, corneal and gag reflexes and their associated cranial nerves. Finally cross sections of myelin stained brain stem sections at classic levels are related to the gross cross sections.

 

10 – Cerebral Circulation (16 minutes) The major vessels of the anterior and posterior circulation are demonstrated along with the Circle of Willis on both a model and in an animation. The distribution of the three major cerebral arteries is demonstrated along with the concept of a watershed zone. A gross specimen with good vessels is also reviewed along with a quick review of primary cortical function.

 

11 – Cortical Localization (13 minutes) The lobes of the brain are defined together with their major functions. The visual field representation in the occipital lobe is explained with a diagram. Speech areas and the major types of aphasia are discussed in the dominant hemisphere and parietal lesions of neglect and spatial orientation are also mentioned. A frontal or coronal section is also outlined demonstrating the somatotopic representation of the body in sensory and motor cortex.

 

12 – Three Critical Vertical Pathways (9 minutes) There is one motor and two sensory pathways that must be mastered. Pain and temperature from the body travel together and vibration and proprioception travel in another pathway each reaching perception in the cortex. Voluntary motor control starts in the cerebral cortex and connects with a motor neuron in the spinal cord or brain stem. Each of these pathways has a different crossing point which is important. With these 3 pathways and your 12 cranial nerves you can localize many diseases.

 

13 – Sensation from the Body (22 minutes) Sensation consists of various modalities, which tend to travel in one of two pathways.  The Anterolateral System also known as the Spinothalamic Tract carries pain and temperature. The Dorsal Column-Medical Lemniscus Pathway carries vibration, joint position, and fine 2-point discrimination. Light or crude touch travel in both pathways. The video demonstrates both grossly and with diagrams the difference in the two pathways as they travel to the cortex emphasizing where they cross to the opposite side. Somatotopic cortical representation and blood supply are introduced.

 

14 – Sensation from the Face (14 minutes) Sensation from the face travels in one of two pathways both of which eventually converge to form the trigeminothalamic tract that reaches the thalamus.  The tract that carries pain and temperature is confusing because it first descends before crossing while the equivalent of Dorsal Column-Medical Lemniscus Pathway carrying vibration, joint position, and fine 2-point discrimination synapses and crosses immediately. The video demonstrates both pathways grossly and with diagrams to its cortical termination.

 

15 – The Most Important Pathway: Motor Control (6 minutes) The origin of the corticospinal tract in the cerebral cortex is traced through gross sections of the hemisphere and brain stem to the spinal cord. Using an animation, the terms upper and lower motor neuron are defined and clinical signs and symptom listed.

 

16 – The Visual Pathway (26 minutes) A brief review of the anatomy of the eye and the photic stimulation of the receptors is followed by a gross exploration of the visual pathway from the optic nerve, chiasm, and tract to the thalamus stressing how the left part of the visual world reaches the right hemisphere. Visual fields are related the retinotopic organization of the visual cortex. The eye as a window to the brain and its important vascular supply is also discussed.

 

17 – Control of the Pupil (15 minutes) Through diagrams, animations and gross specimens the constriction and dilation of the pupil by the autonomic nervous system are described. Both the parasympathetic and sympathetic control are traced and the importance of a constricted pupil, Horner’s Syndrome, and temporal lobe (uncal) herniation (dilation) are emphasized.

 

18 – Control of Eye Movements (18 minutes) Disturbances in eye movements can provide important clues for localization of neurological damage. The role of the frontal eye fields in horizontal gaze is stressed. The need to coordinate cranial nerves on both sides of the brain stem introduces the medial longitudinal fasciculus and its role in coordinating CN 3 and 6. Interruption of this pathway results in internuclear ophthalmoplegia and nystagmus both of which are demonstrated with a clinical video.

 

19 – The Vestibular System (32 minutes) Diagrams, models and skull preparations are used to describe the vestibular apparatus. The semicircular canals, saccule and utricle are described as well as transduction by the hair cells in the ampullae and maculae. Gross material emphasizes the nerve, vestibular nuclei and connections through the MLF to the abducens and oculomotor nuclei in the brain stem for coordinating eye and head movements with body position. Nystagmus, INO, the vestibulocular reflex, and caloric testing are explained. Connections above the midbrain are not discussed.

 

20 – Auditory System (30 minutes) The anatomy of the middle ear and cochlea are shown using models and diagrams explaining the process of air-fluid transmission and finally transduction by hair cells. Gross specimens demonstrate the cochlear nerve and its brain stem relays and crossings all the way to auditory cortex. Wernicke’s area and language comprehension and lateralization are briefly discussed. The Weber and Rinne tests are demonstrated along with radiographs showing normal anatomy and a tumor in the cerebellopontine angle.

 

21 – The Cerebellum (28 minutes) The gross features of the cerebellum are shown. The three peduncles are demonstrated, noting their input and output to and from the cerebellum. Emphasis is given to symptoms of cerebellar disease appearing on the same side of the body. Special emphasis is given to cortical-cerebellar connections, stressing the need for the pathways to cross twice in order to work with the descending corticospinal tract. Cerebellar functions and dysfunctions are discussed while showing clinical examples of patients with cerebellar disease.

 

22 – Basal Ganglia (28 minutes) Structures involved in involuntary movements are shown on models, in animations, and on gross coronal and axial sections. Diagrams show the cortex-to-cortex loop and the nigrostriatal pathway. The direct and indirect pathways are shown. The direct pathway facilitates movement while the indirect pathway inhibits movement on the opposite side of the body. Clinical videos of two diseases, Parkinson’s and Huntington’s, are examples of interruption of the balance between excitation and inhibition in these pathways.

 

23 – Motor Systems (38 minutes) A comparison of the three major motor systems focuses on categorizing motor problems as corticospinal tract, cerebellar, or basal ganglia. It begins with 12 minutes of gross anatomical structures and pathway review followed by clinical video clips demonstrating clinical features of disease of each of the three major circuits. Clinical signs and symptoms include: hemiparesis, spasticity, Babinski, clonus, atrophy, fasciculations, limb ataxia, dysmetria, intention tremor, rapid alternating movements, pendular reflexes, hypotonia, titubation, nystagmus, resting tremor, bradykinesia, athetosis, chorea, tardive dyskinesia, rigidity and retropulsion.

 

24 – Hypothalamus (16 minutes) Gross specimens are used to demonstrate the area of the hypothalamus and its relationship to surrounding structures. Both endocrine and autonomic functions are explored using diagrams. Mention is made of the direct hypothalamic response to circulating hormones and other substances such as sodium.  The differences between anterior and posterior pituitary are described in producing and releasing hormones Finally, descending coordination of autonomic responses is discussed.

 

25 – Olfactory (5 minutes) Beginning with the location of the sensory cells within the skull the axons are traced into the cranial cavity. Demonstration of the olfactory bulb, olfactory tract and it termination in the forebrain and temporal lobe are indicated. Trauma and meningiomas can produce loss of small (anosmia). Degenerative neuronal diseases are often accompanied by loss of neurons in the olfactory pathway resulting in lack of appetite.

 

26 – Limbic (18 minutes) The decision was made to present a simplified description of a much more complex system using animations to construct a 3D image. Papez circuit is shown on gross specimens with mention of its involvement in memory. The role of the amygdala in fear and the olfactory cortex in temporal lobe epilepsy are described. The hippocampus from a brain with dementia is compared with a normal brain.