Neuropsychological Testing - Anatomy notes.
Bits & Pieces
��������������� Double Dissociation - refers to impairment in one system and no impairment in another - the basis for inferring functional modules.
��������������� Complexity of function is directly proportional to its distributedness, hence localized damage affects a few simple functions and a lot of complex ones.
��������������� Brain hypothesis - brain generates behavior.
��������������� Neuron hypothesis - neurons are basic building blocks of consciousness.
��������������� Sections - coronal - through side of face Illustration: Coronal Section of the Brain with Major Structures, saggital - through face Illustration: Saggital Section of the Brain with Major Structures, horizontal. Illustration: Horizontal Section of the Brain with Major Structures
Cytology
��������������� Brain: 180-150 billion cells, 50 billion - neurons, each has up to 50,000 connections; at birth weights 400 gm., at maturity - 1450 gm.; daily dropout rate of neurons 20,000, at 30 dropout=glial growth, then brain mass begins to decrease; brain is 5% of body weight and 20% of its metabolism.
��������������� Astroglia provide support, nutrition and waste product management for neurons, they participate in neurotransmitter metabolism and contribute to the blood-brain barrier (their pseudopodia surround blood vessels in the brain).
��������������� Oligodendroglia form myelin sheets on the neuronal axons increasing the speed of impulse transmission.
��������������� Microglia is mobile and involved in phagocytosis of foreign bodies during an immune response, it also forms scar tissue in the brain.
��������������� Ependymal cells line the central canal of the spinal cord and ventricles, form the choroid plexus where cerebro-spinal fluid is generated.� They might be guiding neuronal differentiation and axonal growth during brain development.
Tumors
Gliomas are 50-60% of intracranial tumors in adults, measured by malignancy from 1 to 4:
Astrocytomas - 50% of gliomas, can be benign or anaplastic, the worst (4) - Glioblastoma Multiformae - classical unoperable malignant tumor;
Oligodendrogliomas - 5% of gliomas, usually slow growing and benign, but can be malignant;
Ependymomas - 5% of gliomas, develop obstructions in CSF flow, may cause hydrocephalia (incontinence, ataxia, progressive dementia).
Meningiomas - 15%, usually supertentorial, slowly growing and benign, increase with age.
Medulloblastomas - more common in kids (20%), tumors of cerebellar cells.
Schwannomas - 6%, twice more common in women.����
Metastatic - 10%, prinary tumor site outside CNS.
Symptoms: focal (depending on the site of lesion); headaches, papilledema, projectile vomiting, drowsiness (due to increased intracranial pressure); seizures (due to irritative impingement on surrounding areas).
Imaging
|
Method |
Characteristics |
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Regional Cerebral Blood Flow (RCBF) |
Isotopes injected into arterial blood, functional |
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CT |
X-ray, anatomical, good for bones, ventricles, large cortical lesions, poor resolution |
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MRI� & PMR |
Protons aligned by magnetic field, anatomical, good resolution |
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Pneumoencephalography |
Air injected in CSF and X-ray taken, anatomical, ventricles - best |
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Ultrasonography |
Ultrasound, anatomical, done a lot on infants |
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Magnetoencephalography (MEG) |
Uses magnetic fields generated by the brain |
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EEG |
Gross measure of electric activity of the brain, mostly cortical synaptic, functional; used for evoked potential studies |
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Single Photon Emission Tomography (SPET) |
Injected with photon emitter or labelled glucose, functional, experimental use based on paired image subtraction |
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PET |
Same as above, only positron emitter is injected - two photons at 90 degrees give better resolution |
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Electromiography |
Measures electrical activity at neuromuscular junctions, functional |
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Neuro Conduction Velocities (NCV) |
Measured to diagnose neuropathy - periferal conduction problems, etc., functional |
Association Tracts Illustration: Association Tracts
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Name |
Connections |
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Anterior & Posterior Comissures |
connect hemispheres in addition to corpus callossum |
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Centrum Semiovale |
axons just under the cortical surfase, connects to corona radiata |
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Corona Radiata |
connects to corpus callossum & basal ganglia |
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Corpus Callossum |
connects hemispheres, myelinates anterior to posterior (as opposed to the rest of the brain) |
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Articulate Fasciculus |
connects Wernicke�s and Broca�s |
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Internal Capsule |
association fibers of cerebellum, thalamus an basal ganglia in addition to major afferent & efferent pathways from spinal cord and brain stem to hemispheres |
Subcortical Nuclei: coordinate fine motor movement and responsible for automatic motor skills, lesions produce fine tremors along the limb axis and disturbances in muscle tone, also called Basal Ganglia and Extrapyramidal system, together with cortex are called Telencephalon. Illustration: Brain Stem
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Name |
Notes |
Functions |
Lesions |
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Caudate Nucleus |
connected by cell bridges to putamen |
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called Huntington�s chorea: rapid, jerky, nonrithmic tremors (extremeties mostly) and dementia |
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Putamen |
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Striate Nucleus |
Caudate + Putamen , CABA neurons |
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Globus Pallidus |
consists of 2 lobes connected by lamina |
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Lentiform Nucleus |
Putamen + Globus Pallidus |
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Amygdala |
8 subnuclei |
generates emotions from perceptions and thoughts |
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Hippocampus |
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consolidates new information, turning short-term memory into long-term |
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Claustum |
the bottom of the whole thing |
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Brain Stem (unilateral lesions produce ipsilateral cranial nerve signs and contralateral motor or sensory signs; RAT is in tegmental portion of the whole brain srem, it regulates level of activity in conscious, visceral, endocrine, vascular, and motor systems):Illustration: Brain Stem
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Name |
Notes |
Functions |
Lesions |
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DIENCEPHALON - Thalamus + Hypothalamus |
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THALAMUS - 33 subnuclei, relays sensory info to cortex (Saggital: 1) |
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Epithalamus |
on top, contains pineal gland which calcifies with aging (easy to see on scans) |
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Thalamic syndrome - peculiar contralateral sensory phenomena |
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Lateral Geniculate |
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visual processing |
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Medial Geniculate |
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auditory processing |
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Pulvinar |
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somesthetic relay |
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Mammilary bodies |
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memory |
in Korsakoff�s |
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Hypothalamus |
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temperature control, emotions, autonomic nervous syst. control, metabolism, electrolyte balance |
diabetis, bulimia, other metabolic diseases, sexual disfunctions, temperature control and sleep disturbances, convulsions with visceral symptoms |
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MIDBRAIN = mesencephalon, Aqueduct of Sylvius separates it into Tectum & Tegmentum, lesions lead to unconsciousness, coma, death. (Saggital: 4) |
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Tectum |
on top, contains superior & inferior colliculi - Corpora Quadrigemina |
superior - visual (blind vision), inferior - auditory |
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Tegmentum |
on bottom, Red Nuclei + Substantia Nigra + Bases Pedanculorum |
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Red Nuclei |
origin of Rubrospinal motor system |
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Substantia Nigra |
dopamine |
pyramidal system |
Parkinson�s - pyramidal symtoms |
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Bases Pedanculorum = Crus cerebri |
Corticospinal tract, Frontopontine, & Ocipitobulbarpontine tracts pass through |
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Metencephalon = Pons + Cerebellum |
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Pons |
has 6 cerebellar connections: superior, middle, & inferior cerebellar peduncles |
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Cerebellum |
two hemispheres connected by Vermis; archicerebellum - floculonodular lobe - frontal - equilibrium; paleocerebellum - anterior lobe & part of vermis - muscle tone; neocerebellum - posterior lobe & most of vermis - synergy; dentate, emboliform, fastigial, & globose nuclei |
synergy - gross coordination of voluntary movement, equilibrium, muscle tone, procedural memory |
ipsilateral damage, dysmetria = ipsilateral, coarse flailing tremor along the limb axis, ataxia - staggering producing wide gate, dysdiadochokiesia - rapid alternating movements of opposing muscle groups, fall in thye direction of the lesion, round heel syndrome - falling backwards if vermis is lesioned |
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Medulla = Mylencephalon |
corticospinal tract decussates half way down it |
respiratory and cardiac centers |
coma, death |
Spinal Cord - 31 pairs of nerves come out from intervertebral foramena (first one comes over the top of V1); on the bottom Conus Medullarus is connected by Filum Terminale to dura to hold spinal cord in place; central canal on ventral side is lined with ependymal cells; afferent (sensory) neurons go through dorsal roots with primary neuron body in spinal ganglia, efferent (motor) neurons go through ventral roots; fibers that crossed over in medulla form the lateral bundle of CST (corticospinal tract), UMN (upper motor neurons) of CST are inhibitory and go down to where they would leave the cord, there they connect in the ventral horn with a number of LMNs which are excitatory. Illustration: Sensory and Motor Pathways
Symptoms of Lesions in CST:
|
# |
UMN |
LMN |
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1 |
initially flaccid paralysis leading to spastic after a few days or hours |
flaccid paralysis from the beginning |
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2 |
hypertonicity |
hypotonicity |
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3 |
hyperreflexia� - knock-on-joint� or deep muscles reflexes (4-4+ when graded on 1-4 strength scale) |
hyporeflexia |
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4 |
Babinsky |
no Babinsky |
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5 |
no fibrillation (little twitches in muscles) or fasciculation (microscopic twitches) |
constant fibrillation & fasciculation, especially if muscles are exercised |
���������������
Reflexes:
1.� Superficial
a)� Mucus:
-� Corneal - blink reflex;
-� Pharingeal - gag reflex;
-� Uvular;
-� Sneezing.
b)� Skin (all diminish with UMN lesions):
- Abdominal twitching (when touched);
-� Interscapular twitching;
-� Cremasteric (testicles rise when inner thigh is stroked);
-� Gluteal;
-� Planter;
-� Anal winkle.
2.� Deep
a)� Muscles (graded 1-4, especially looking for lateralization, if no reflex yank them on the arm):
-� Maxillary (if you tap down on a pen between teeth, lower jaw rebounds);
-� Biceps;
-� Wrist;
-� Patellar;
-� Achilles.
b)� Visceral:
-� Pupillary (narrows with light);
-� Consensual light (right eye blinks when light� shines on the left one);
-� Accomodation reflex;
-� Blink reflex of Descartes (blink when finger is suddenly brought near to the eye);
-� Mass reflex or reflex of Reddoch (in people with complete section of the spinal cord
stimulation below lesion causes complete flexion of all muscles & incontinence).
3.� Pathological = Frontal release = Cortical release - all normal in kids but get inhibited with growing myelination
a)� Babinsky (flaring toes going up when sole is stroked, normal in kids untill 5 years).
b) Grasp (upon stroking the palm), more subtle frontal signs (affected by alcohol, tiredness, etc.): give pt. two fingers and ask to squeeze them on red, not green, then say: � red, green, GREEN�, if pt. squeezes on second green - positive.
c)� Hoffman�s (thumb goes in a lot if you flick a finger on relaxed hand).
d)� Globella (tap between eyebrows, if there�s no habituation after 2-3 times - positive).
e)� Snout (put finger under pt�s nose and tap - pluckered lips).
f)� Rooting reflex.
Overview of Motor Tracts (Efferent - ventral roots): Illustration: Sensory and Motor Pathways
|
System |
Lateral (limb/distal movements) |
Anteriomedial/Ventromedial (trunk/proximal movement control) |
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Tract |
Lateral Corticospinal (2) |
Rubrospinal (3) |
Anteriomedial Corticospinal (6) |
Vestibulospinal (5) |
Reticulospinal (4) |
Tectospinal |
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Lateralization |
contralateral |
contralateral |
ipsilateral |
ipsilateral |
ipsilateral |
contralateral |
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Function |
limb control |
flexor tone control |
axial muscles control |
posture & balance control |
controls rapid orientation & coordination of muscles |
orientation to visual stimuli before conscious reaction |
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Notes |
decussation of the pyramids - Medulla |
anterior Tegmental decussation |
decussate in the cord - anterior comissure, terminates in toracic region |
starts in vestibular nuclei of Pons and Medulla |
lateral strand begins in RAS in Medulla, medial - in RAS in Pons |
posterior Tegmental decussation, starts in superior colliculi |
Sensory Systems:� General sensory systems include: touch & pressure - exterioception, position - proprioception, temperature & pain - noceoception;� Special systems include vision, hearing, taste, smell, balance;� Dermatome = area of the skin sending info into the same spinal nerve. Sensory and Motor Pathways Page
Overview of Somesthetic (Afferent) Tracts (dorsal roots, tertiary neurons from all but muscle tone tract go to the cortex): Illustration: Sensory and Motor Pathways
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Sense |
1st neuron in |
2nd neuron in |
Spinal tract |
Side |
2nd neuron�s synapse |
Decussation |
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pain / temperature |
posterior root ganglion |
posterior horn |
Lateral Spinothalamic (7) |
contralateral |
Thalamus |
anterior comissure of spinal cord |
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crude touch / pressure |
posterior root ganglion |
posterior horn |
Anterior Spinothalamic (7) |
bilateral |
Thalamus |
anterior comissure of spinal cord, only 50% cross over |
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fine touch / pressure / joint position sense / vibratory sense |
posterior root ganglion |
Nucleus Gracilis & Nucleus Cuneatis in Medulla |
Posterior columns: Fasciculus cuneatis (arms), Fasciculus Gracilis (legs)(behind 9) |
ipsilateral up to Medulla |
Thalamus |
Medulla, decussation of the Trapezoid body |
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muscle tone |
posterior root ganglion |
Nucleus Dorsalis (nuclei Dorsalis form the Clark�s column together) |
Spinocerebellar tract (8, 9) |
ipsilateral |
Cerebellum |
none |
Spinal Cord Syndromes:
|
Name |
Damage |
Symptoms |
|
Brown-Sequard syndrome |
hemisection of the cord |
below the level of the lesion ther�s ipsilateral: spastic paralysis, loss of fine touch, sweating, and position sense; contralateral: loss of sense of pain & temperature |
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Anterior Poliomyelitis |
inflammation of the anterior portion of the cord |
below the level of the lesion ther�s bilateral: flaccid paralysis, decreased pain and temperature sense |
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Posterior Cord disease |
any lesion |
lose positional sense and vibration, report bizzare sensations |
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Bulbar lesions |
brain stem lesions |
tongue protrusion may be transiently affected (it deviates from midline), contralateral: paralysis of face, leg, arm (torso, chewing, swallowing, phoneting, & upper face are spared unless damage is bilateral) |
�
Meninges:
1)� Dura mater = Pachymenix consists of two layers which are tightly attached to eash other, Endosteal = Periosteal layer adheres to the scull, Meningeal layer separates from it to form partitions = Falx and Sinuses and to go down through Foramen Magnum, where this is the only Dura layer, subdural space is narrow, filled with lubruicant.
2)� Arachnoid layer consists of connective tissue and a lot of vasculature, it is connected to Pia by Arachnoid Trabeculations, subarachnoid space is filled with CSF, large spaces are called cisterns, Arachnoid Granulations are groups of absorband cells which transfer CSF from cisterns into sinuses (they are very sensitive to mild head injuries).
3)� Pia mater - fuses with the surface of the brain; forms Dentate ligaments attached to Arachnoid in spinal cord.
4)� Leptomeninges = Arachnoid + Pia, they have two types of meningitis: pyogenic = bacterial and lymphocytic or aceptic = viral.
CSF:� 100-160 ml., produced at the rate of 50-500 ml. a day, cushions brain & removes waste products, sterile, pressure is 80-180 mm. of H2O, produced in Choroid plexus (ependymal cells) in all ventricles.Illustration: Ventricles
Cerebral Cortex
Functions & Symptoms:
Numbers in the table below refer to the Broadmann Map
Illustration: Cortex - Side view
Illustration: Cortex - Base
|
Lobe |
Area |
Function |
Lesion |
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Frontal |
Primary Motor (4) |
initiates contralateral voluntary movement - gross |
destructive: contralateral flaccid turning into spastic paralysis test: grip strength (>20% discrepancy between hands) |
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Transitional (betw. 4&6) |
inhibit motor activity, extrapyramidal functions, frontopontocerebellar pathway beginning (conscious control over degree of movement coordination) |
destructive: spasticity of contralateral muscles, paresis (weakness), ataxia |
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Secondary or Premotor (6) |
organize & control voluntary movement, esp. series of movements (walking) |
destructive: spasticity of contralateral muscles, paresis, problems with complex coordinated movements |
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Motor Eye Field (8&46) |
control voluntary conjugate eye movement |
destructive: transient deviation of eyes towards the lesion irritative: permanent deviation of eyes away from the lesion |
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Speech - Broca�s |
control expressive speech in dominant hemisphere, non-semantic expressive elements of speech in the other one |
destructive: motor/expressive aphasia in dominant, expressive aprosodia in the other one |
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Prefrontal Association or Tirtiary (9,10,45,47) |
high intellectual processes, emotions (connections to Thalamus & Hypothalamus), elaborate voluntary movements (connections to basal ganglia) |
destructive: psychomotor retardation, indifference, personality change (loss of social inhibitions, initiative, planning, attention, abstact thinking, flat affect) |
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Cingulate (24&25) |
see Temporal lobe |
see Temporal lobe |
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Parietal |
Primary Sensory (1,2,3) |
receive, identify, & localize gross somatosensory input (contralateral) |
destructive: contralateral impairment of somesthetic sense, complexity increases 3-1-2 |
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Secondary Association |
integrate, synthesize, and elaborate somesthetic input |
destructive: slight contralateral impairment of somatic sensation (two-point threshold), astereognosis (inability to differentiate objects by touch) |
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Posterior part of 7 |
further integration & fine discrimination of somesthetic input |
same as above + inattention (supression/extinction test), trophic lesions, graphestesia test problems (discrimination of shapes written on skin) |
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Angular gyrus (39) & Supramarginal gyrus (40) |
integrate visual and auditory stimuli with somesthetic input |
destructive: in dominant hemisphere receptive aphasia, alexia, agraphia, body scheme defect; Gerstman Syndrome: finger agnosia (don�t know which finger was touched), acalculia, right/left disorientation, & agraphia |
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Gustatory (43) |
gustatory input |
destructive: none - bilateral irritative: strange, unpleasant tastes |
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Cingulate (23,31) |
see Temporal lobe |
see Temporal lobe |
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Subcortical optic radiations |
visual information to cuneate gyrus |
destructive: contralateral homonimous inferior quadrantopsia |
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Temporal |
Primary Auditory Receptive or Heschl�s gyrus (41,42) |
receive auditory impulses, larger in dominant hemisphere, includes Planum Temporale |
destructive: none- bilateral |
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Association, Wernicke�s (22,42) |
complex sound processing (meaning, syntax, etc.), memory, vestibular coordination |
destructive: dominant - receptive aphasia, other - receptive aprosodia |
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Olfactory (28,35) |
olfactory information |
destructive: none-bilateral irritative: psychomotor seizures, unpleasant olfactory hallucinations |
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Association (20,21,36, 37,38) |
form connections to other lobes, involved in memory formation and other complex functions |
irritative (temporal seizures): deja vu or feeling that familiar things became new in both hemispheres, overwhelming fear without cause - left hemisphere only |
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Cingulate (29,30,31, 24,25) |
control visceral phenomena, sexual activities, emotions |
destructive (large bilateral lesions): personality changes, disinhibition, recent memory impairment, Kluver-Busy syndrome: talk a lot, sexually fixated, eat a lot, unable to ignore novel stimuli (hypermetamorphosis) irritative: psychomotor seizures |
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Subcortical optic radiations |
visual information to lingual gyrus |
destructive: contralateral homonimous superior quadrantopsia |
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Occipital |
Primary Visual (17) |
contralateral visual input |
destructive: contralateral homonimous hemianopsia with mavular sparing, bilateral lesion - cortical blindness |
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Parareceptive, Secondary Visual (18) |
interpret visual impulses, optical reflexes, �what� pathway - temporoocipital, �where� pathway - parietooccipital |
destructive: disturbance of spatial orientation & discrimination, visual agnosia, illusions, hallucinations (well-formed but don�t feel real) |
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Preoccipital (19) |
visual associations: perception, orientation, recall, optical reflexes |
transient conjugate deviation of eyes toward the lesion, simultagnosia, visual perseveration, supression/extinction |