NEURO: Quiz 2 Flashcards
Hematomas
1) Epidural
Arterial blood in space causes pressure on cerebral hemisphere, causing herniation of brain into foramen magnum; 15-20% are fatal
(2) Subdural
Venous blood in space, due to tearing of bridging veins; lower pressure blood thus filling is slow space; less likely herniation of brain into foramen magnum
(3) Subarachnoid
Hemorrhage (may be from aneurism), usually arterial), but larger volume can accommodate more blood in space
Cerebrospinal fluid movement
Production:
Choroid plexus
600 ml/day
Circulation:
Total volume = 150 ml
80% in subarachnoid space, 20% in ventricular system
Ventricular system – Medial and lateral apertures – Subarachnoid space – Superior sagittal sinus – Venous system
Reabsorption:
Arachnoid granulations in SSS
Pressure gradient pushes CSF into sinus
Turn over = 600/150 ml/day = 4x/day
Herniations
(1) Subfalcine = Accumulation of blood (e.g., hematoma) or tumor in upper skull pushes brain under falx cerebri
(2) Uncal = Bleed in temporal lobe pushes brain around tentorium cerebelli
(3) Foramen magnum = Tumor or vascular problem in cerebellum pushes tonsils of cerebellum through foramen, squishes medulla (impairs respiratory centers), and blocks CSF (e.g., hydrocephalus)
Hydrocephalus
= Excess CSF due to one of 3 causes:
(1) Oversecretion by choroid plexus (rare)
(2) Impaired absorption by arachnoid granulations (may be congenitally absent) (very rare)
(3) Obstructed flow at narrowings in ventricular system
Most common
Interventricular foramen, cerebral aqueduct, or medial and lateral apertures (all 3 must be blocked)
Communicating = No blockage within ventricular system, but CSF cannot get out of subarachnoid space into sinuses due to blockage of arachnoid villi Noncommunicating = Passages between ventricles have been blocked (i.e., ventricles cannot "communicate" with each other)
Forebrain
(1) Diencephalon
– Thalamus
– Hypothalamus
= Integration of info passing from brainstem and spinal cord to cerebral hemispheres, as well as integration of motor and visceral activities
(2) Telencephalon
– Cerebral hemispheres
= Integrate highest mental functions (e.g., awareness of sensations and emotion, memory and learning, intelligence and creativity, and language)
Diencephalon
(1) Thalamus = Relays sensory impulse to cerebral cortex
- - Interthalamic adhesion = connects R and L thalamic lobes (third ventricle between)
(2) Hypothalamus = Regulates body temperature, certain metabolic processes, and other autonomic functions
- - Attaches infundibulum of pituitary gland
NOTE: Both contain gray matter nuclei and white matter tracts
Cortical connections
= White matter pathways that connect gray matter regions of cerebral hemispheres
(1) Intracortical = connect area of one gyrus to other area of same gyrus
(2) Association = connect one gyri to another
- - Short = connect gyri within same lobe
- - Long = connect gyri between two different lobes
(3) Commissural = connect homologous areas of two hemispheres (e.g., corpus callosum)
(4) Projection = connect cerebral cortex with subcortical nuclei through internal capsule
- - Internal capsule = white matter region between thalamus and basal ganglia
Association fibers
Short = connect adjacent gyri (same lobe)
Long = connect gyri between lobes:
(1) Superior longitudinal fasciculus = many connects among all except limbic lobe
(2) Arcuate fasciculus = sub-component of SLF connects temporal and frontal language areas
(3) Inferior occipitofrontal fasciculus = connects occipital, temporal, and frontal lobes
(4) Uncinate fasciculus = connects frontal and temporal lobes
(5) Cingulum = associated with limbic system
Commissural fibers
= Connect homologous regions of two cerebral hemispheres
(1) Corpus callosum = connects L and R frontal, parietal, temporal, and occipital lobes
(2) Anterior commissure = connects middle and inferior temporal gyri (anterior portion of brain)
Projection fibers
= Connect cerebral cortex with subbcortical nuclei (gray matter) via internal capsule
(1) Corticofugal = efferent fibers carry motor signals away from cortex
(2) Corticopetal = afferent fibers mainly connect thalamus to areas of cerebral cortex
Frontal lobe functional areas (6)
(1) Primary motor (Area 4 or MI): Discrete voluntary (fine motor) movements on contralateral side (e.g., finger tapping)
- - Partly overlaps with precentral gyrus
(2) Premotor (lateral Area 6): Gross movements (whole extremities) involving lots of muscles on contralateral side
- - Part of precentral, superior, middle, and inferior frontal gyrus
- - Contains programming necessary for movement
(3) Frontal eye field (lateral Area 8): Conjugate eye movements to contralateral side
- - Just anterior to Area 6
(4) Supplemental motor (medial Areas 6 & 8): Complex movements involving several parts of body (e.g., orientation of body and head toward object for reach and grasp)
(5) Prefrontal (in front of 6, 8, and 45):
- - Orbital = emotion, behavior and olfaction (just above orbit)
- - Lateral = intellectual abilities (conceptualizing, planning, judgement, and problem solving)
(6) Motor language (Broca’s) (Areas 44 & 45) = Motor language area
- - Word and speech production
Parietal functional areas (3)
(1) Primary somatosensory (SI or Areas 3, 1, 2): Tactile discrimination and position sense on contralateral side (= localization)
- - Most of postcentral gyrus
(2) Secondary somatosensory (SII): Somewhat uncertain role
- - Likely perception of info from SI and perception of pain (= perception)
- - Continuous with post central gyrus and overlies insula in lateral fissure
(3) Parietal association (Areas 5,7,39, and 40): Integration or processing of tactile and visual information
- - Cognition of body and objects surrounding it (= processing/integration)
- - Involved in neglect syndrome
- - Between postcentral gyrus and occipital lobe
- - Some overlap with supramarginal and angular gyri
Temporal lobe functional areas (3)
(1) Primary auditory cortex (Areas 41 & 42 or A1 & A2): Hearing
- - Although damage to one side causes minimal effects (difficulty locating sound) because of the bilateralism of auditory pathways
- - Transverse temporal gyri within lateral fissure
(2) Auditory association area (Wernicke’s area) (Area 22): Receptive language area (dominant side)
- - Involved with language comprehension
- - Associated with supramarginal gyrus
(3) Areas associated with emotions and higher mental functions (memory and speech)
- - Strongly associated with limbic system
- - Dominant side = storage of auditory information
- - Non-dominant side = storage of visual information
Occipital lobe functional areas (2)
(1) Primary visual cortex (Area 17 or VI): Initial visual processing
- - Segregation of visual information into its component elements (orientation, depth, color, motion)
- - Distribution of signals to visual association areas
- - Occipital pole and medial surface between parts of Area 18
(2) Visual association areas (Areas 18 and 19): Complex visual perceptions
- - Related to color, movement, and orientation of objects
- - Lateral side anterior to Area 17, medial side superior and inferior to Area 17
Dominant hemisphere
= Centers for language comprehension and production
- Language function (verbalization)
- Mathematical ability
- Ability to solve problems in a logical manner
– Damage to this hemisphere causes aphasia (difficulty speaking)
NOTE: 90-95% are L hemisphere dominant (regardless of handedness)
Non-dominant hemisphere
= Centers for:
- Spatial perception and awareness
- Emotional (non-verbal) aspects of language and communication
- Musical skills
- Facial recognition
- Ability to perform tasks that require comprehension of spatial relationships
NOTE: Damage to this hemisphere causes hemispatial neglect of opposite side of body (e.g., L side neglect)
Language centers
Both located in DOMINANT hemisphere, connected by arcuate fasciculus :
(1) Broca’s area (Areas 44&45) = motor language area
- - Contains motor programs for word production
- - Communicates with motor cortex that controls muscles involved with articulation and other forms of language expression (e.g., sign language, writing)
- - Associated with expressive aphasia (non-fluent)
- - Slow speech, poor ability to generate words, and short sentences
(2) Wernicke’s area (Area 22) = sensory or receptive language area
- - Involved in comprehension and formulation of language
- - Associated with receptive aphasia (fluent)
- - Normal production of words, but words lack meaning
- - Normal rhythm and intonation, but deficits in language comprehension of any form
- - Heard, read, or spoken
- - May have trouble interpreting gestures or figures of speech
Global aphasia = both areas and fasciculus affected
NOTE: High variability in extent and nature of how people are affected
Blood brain barrier
= Diffusion barrier that protects brain from compounds, chemical fluctuations, and infections in the bloodstream
– Allows diffusion of certain small molecules (e.g., O2, CO2, nicotine, ethyl alcohol) and selective (active) transport of large molecules (e.g., amino acids, insulin, glucose)
Components:
- Endothelial tight junctions (no fenestrations)
- Basement membrane
- Astrocyte foot processes (metabolic support of endothelial cells)
Circle of Willis (posterior to anterior)
Posterior:
Vertebral arteries (2)
– Posterior inferior cerebellar arteries (2) (PICA)
Basilar artery (1) (BA)
– Anterior inferior cerebellar arteries (2) (AICA)
– Internal acoustic or labyrinthine arteries (2) (15% off of basilar a.)
– Superior cerebellar arteries (2) (SCA)
Posterior cerebral arteries (2) (PCA)
– Posterior communicating arteries (2) (Pcomm) (connects to anterior part via MCA/ICA)
Anterior:
Internal carotid arteries (2) (ICA)
-- Middle carotid arteries (2) (MCA)
--- Lenticulostriate arteries
-- Anterior carotid arteries (2) (ACA)
--- Anterior communicating arteries (Acomm) (connect two ACA)
Arterial pathway (heart to Circle of Willis)
Heart
- Aorta
- Subclavian artery
- – Vertebral arteries (through transverse foramina, suboccipital triangle, foramen magnum)
- – Basilar artery
- – Posterior cerebral arteries
- Posterior communicating arteries – ICA
- – Posterior cerebral arteries
- – Basilar artery
- – Common carotid
- – Internal carotid (through carotid canal)
- Posterior communicating arteries – PCA
- – Internal carotid (through carotid canal)
Transient ischemic attack (TIA)
= Transient loss of function due to blockage of blood supply to any region of the brain
- Clot removed by body and supply restored
- May have some permanent damage depending on extent of necrosis
- # 1 predictor for impending CVA
NOTE: Ischemic = tissue death or necrosis due to loss of blood supply
MCA stroke
Structures:
Lateral aspects of cerebral hemispheres
Primary motor (lateral Area 4)
Primary somatosensory (lateral Area 3, 1, 2)
Sensory association cortex (secondary somatosensory area)
Pre-motor cortex (lateral Area 6)
Frontal eye field (lateral Area 8)
Dominant side: Broca’s/Wernicke’s (Areas 44, 45)
Functions:
Contralateral hemisensory loss (somatosensory cortex damage)
Contralateral hemiplegia/hemiplasia (motor cortex damage)
– UE/face affected more than LE (lateral side) (motor and sensory)
Dominant hemisphere damage (usually L) = aphasia (speech and comprehension)
Nondominant hemisphere damage (usually R) = hemispatial neglect
ACA stroke
Structures:
Medial frontal and parietal areas
Primary motor (medial side Area 4)
Primary somatosensory (medial side Area 3, 1, 2)
Supplemental motor (medial sides of Areas 6 & 8)
Paracentral lobule (medial side of pre- and postcentral gyri)
Precuneus (medial side between para central lobule and parietooccipital sulcus)
Cingulate gyrus
Corpus callosum
Functions:
Contralateral hemiplegia/hemiplasia (motor area)
Contralateral hemisensory loss (somatosensory area)
– LE/trunk more than upper extremity (medial side) (motor and sensory)
Limbic system deficits
PCA stroke
Structures: Medial and inferior occipital lobe -- Cuneus (parts of Areas 18 & 19) -- Inferior and superior calcarine cortex (Areas 17, 18) Inferior temporal lobe Midbrain (upper brainstem) Thalamus
Functions:
Visual field deficits (primary visual cortex and visual association areas)
– Cortical blindness
– Complete or partial loss of vision in normal appearing eye
Thalamus information relay affected (inability to process sensory input)
– Every type of sensation impaired
– Lack of proprioception (e.g., tremors)
Auditory processing deficits (temporal lobe)
Vertebro-Basilar stroke
Structures: Pons Medulla Cerebellum Cranial nerve nuclei Thalamus
Functions: Vital centers necessary to maintain life (e.g., breathing) Dysphasia (impaired swallowing) (CN X) Vestibular system (CN IX) Eye movement (nystagmus) (CN III, IV, VI) Dizziness, vomiting, nausea Poor balance (CN IX) Cranial nerve function
NOTE: Uncommon, high mortality, poor functional outcome; location and size determines whether ipsilateral, contralateral, or both sides affected (above or below crossing of corticospinal tracts)
Watershed regions
= Borders between arterial vascular distributions
– Areas at risk for ischemic stroke, especially during hypotensive events (low BP)
Small branches of MCA and PCA
MCA
(1) Lenticulostriate = “penetrating arteries” branch off MCA near its junction with ICA, supplying blood to basal ganglia and internal capsule
- Microvascular disease in these arteries can result in “lacunar infarcts” (i.e., tissue necrosis due to occlusion of penetrating artery)
- Common cause of ischemic strokes (25%)
- Cause lesions of thalamus, basal ganglia, and internal capsule
(2) Anterior choroidal artery = branch off MCA, supplies choroid plexus of lateral ventricle
(3) Posterior choroidal arteries = branches off PCA, supplies choroid plexus of lateral ventricle
Spinal cord arterial supply
Superiorly:
Vertebral arteries
– Anterior spinal artery = single branch runs up anterior center of cord
– Posterior spinal arteries = two branches on posterior side
Inferiorly:
Posterior intercostal arteries
– Radicular arteries
– Anterior and posterior spinal arteries
Posterior spinal artery = posterior 1/3 of cord (posterior funiculus & sometimes posterior horns)
Anterior spinal artery = anterior 2/3 of cord
