Section 1 Flashcards
Symptoms in the head (e.g., facial weakness) usually rule out what?
spinal cord (Horner’s is the exception).
Increased tone usually rules out what?
pathology that is strictly peripheral
If in the brain, what level is the lesion?
Shift your diagnosis rostrally to accommodate additional reported symptoms. Do not shift down (caudally).
If the symptoms occur suddenly, they are most probably caused by what?
a stroke, except if caused by obvious trauma.
Strokes can be either
hemorrhagic or ischemic (thrombus).
If the symptoms progress gradually over time and are unilateral, they are likely caused by a
tumor.
Tumors often are accompanied by
increased intracranial pressure, although large hemorrhagic strokes can also present with increased intracranial pressure.
Symptoms caused by a disease process develop gradually and are usually
bilateral in nature with no increased intracranial pressure.
If the lesion is in the spinal cord:
All sensory and motor symptoms are on the same side as the lesion except loss of pain and temperature.
If the lesion is in the brain stem:
The lesion is on the same side as the highest symptom (the one which located the level); lower symptoms will occur on the opposite side.
If the lesion is in forebrain,
all sensory and motor symptoms are on the opposite side of the body (olfactory loss is the exception).
If the lesion is in the cerebellum (or its input or output tracts)
all symptoms are on the same side as the lesion.
Reduce all somatosensory words (loss of pain, position sense, temperature, joint sense, etc.) into
one symptom, “sensory loss of the … [e.g., left trunk and limbs].” Somewhere along its course the ascending sensory pathways have been cut.
Reduce all motor symptoms to one of three diagnoses:
1) Failure to move: includes “paralysis, paresis, weakness, hypertonus, spastic, flaccid.” All of these indicate lesion of descending motor pathways (motor cortex, internal capsule, descending motor tracts, etc., motor neurons.). 2) Tremor, incoordination, usually implicate cerebellum 3) involuntary, uncontrollable movement implicates basal ganglia
telencephalon =
cerebral hemispheres (cortex + white matter + basal ganglia)
diencephalon =
thalamus + hypothalamus
mesencephalon =
midbrain
metencephalon =
cerebellum + pons
myelencephalon =
medulla
forebrain =
telencephalon + diencephalon
hindbrain =
metencephalon + myelencephalon (i.e. cerebellum + pons + medulla)
brainstem =
midbrain + pons + medulla
The glossopharyngeal, vagus, hypoglossal, and spinal accessory nerves originate largely in the
medulla
Collectively, what do the glossopharyngeal, vagus, hypoglossal, and spinal accessory nerves do?
they control breathing and heart rate (among other things) so that ataxic or disrupted breathing (death), or irregular heartbeats suggest that the medulla has been compromised by the patient’s illness.
ataxic or disrupted breathing (death), or irregular heartbeats suggest that
the medulla has been compromised by the patient’s illness.
Cranial nerves 5, 6 and 7 originate in the
pons,
so that loss of sensation in the face, or an eye deviated medially, or weakness of the facial muscles is often indicative of
pontine dysfunction.
Cranial nerve eight originates in
the transition between the pons and medulla, and
CN 8 symptoms include
ipsilateral deficits in hearing or balance.
Cranial nerves 3 and 4 originate from the
midbrain.
Midbrain dysfunction often shows as
a dilated pupil or an eye whose movements are extremely restricted (Cn 3).
Additionally, levels of consciousness are controlled by circuits in the
tegmentum of the midbrain so a coma usually indicates forebrain or midbrain involvement.
Cn 1 and 2 are
forebrain nerves.
Loss of smell or the more common loss of vision indicates
forebrain disease.
Changes in “mental” functions, memory, language, affect also indicate
forebrain disease.
The cerebral cortex
participates in many sensory, motor, and “cognitive” processes and is the largest component of our brain, about 85% of the brain by weight.
The surface of the cortex is
highly convoluted into gyri and sulci, which are similar from person to person and define general functional regions.
The cerebral cortex is interconnected with the other side of the brain via
commissures, including different parts of the corpus callosum, and the anterior commissure.
Most of the cerebral cortex is made up of
neocortex
Neocortex
contains neurons organized in six layers or laminae that are numbered from the surface of the brain to the deep white matter.
Each layer (of the neocortex) has
neurons with distinctive morphology.
Changes in the organization of these laminae (number of neurons, cell packing density, perikaryal size, etc.) between different cortical areas is related to
their functional specialization; altogether over 50 subdivisions of the cortex have been defined by these histological differences
For instance cortical layer IV is made up of
small stellate neurons with locally ramifying axons.
In sensory cortices
(somatosensory, visual, auditory) this layer is prominent and receives input from the thalamus.
Layer V is
prominent in motor cortex and contains large pyramidal cells, whose axons leave the cortex to descend to the brainstem and spinal cord.
Layer IV is
difficult to detect in motor cortex.
In addition to this laminar organization, connections of groups of neurons between different laminae are
organized in a vertical or columnar fashion, so that cells with similar function tend to span all cortical layers within these columns.
In sensory and motor regions of cortex, this columnar organization is
represented topographically across the surface of the cortex.
Sensory cortex
(post-central gyrus) a map of the body’s surface spreads over this region such that columns of neurons representing the face is located within this gyrus in a region near the lateral fissure, the arm more superiorly, and the leg and foot representation ar
Occipital lobe
Its functions are associated with the visual system and damage to it result in visual deficits.
Visual information
(from the thalamus) to the cortex comes first to the primary visual cortex (often called “area V1” or “area 17”).
V1
This region of the occipital cortex includes a portion of the lingual and cuneate gyri and within the deep folds of the calcarine sulcus.
Most of the primary visual cortex is on
the medial surface of the hemisphere
Visual information after the primary visual cortex
then spreads to other portions of the occipital cortex and to areas in the parietal and temporal lobes (e.g. areas 18 and 19).
Lesions in the occipital lobe usually cause
blind spots (called “scotomas”) in the half of the visual field contralateral to the lesion.
Each side of the visual cortex is
interconnected with the other side via the splenium of the corpus callosum.
Parietal Lobe parts
- Postcentral gyrus 2. Superior parietal lobule 3. Inferior parietal lobule
- Postcentral gyrus -
This area is associated with the somatosensory system.
Post central gyrus is analogous to
area V1 of the occipital cortex in that it is the site where somatosensory information from the thalamus first reaches the cerebral cortex.
Post central gyrus is also called
area “SI” or Brodmann’s areas 3,1, 2
Damage to Brodmann’s area leads to
somatic sensory deficits (e.g. loss of touch, limb position) on the opposite side of the body.
Because of the topographic localization of sensory information within the postcentral gyrus, damage to a portion of it (e.g. anterior cerebral artery infarct damaging the medial aspect of the cortex) will result in
sensory loss to only a portion of the opposite side of the body and help to localize the damage.
Superior parietal lobule -
This region is associated with guiding movement.
Lesions of the superior parietal lobule
will sometimes cause “apraxia”. This is an inability to bring the limb under sensory or cognitive control.
Example of apraxia
a patient may not be able to point to an object when asked, even though he can see it clearly, and his limbs are not paralyzed.
Inferior parietal lobule –
This region is associated with several cognitive functions.
Inferior parietal lobule in the “dominant” hemisphere
(usually the left) it is concerned with language.
The supramarginal gyrus is
part of “Wernicke’s area” and is needed to understand language
The angular gyrus
is the gateway through which visual information reaches Wernicke’s area.
Damage to the angular gyrus
area affects the ability to read.
In the right hemisphere, pathology of this same area as the angular gyrus leads to
spatial disabilities; 1) The patient gets lost even in his own home. 2) He may display “neglect”, forgetting to dress or shave the left side of his body, and he may not notice anyone standing to his left. 3) In severe cases he may even deny that the left
Corpus callosum
The parietal lobe and posterior parts of the frontal lobe are interconnected through the body of the corpus callosum.
Temporal Lobe:
1) heschl’s gyrus / gyri 2) superior temporal gyrus 3) Middle, inferior, and occipito-temporal (fusiform) gyri 4) Parahippocampal gyrus and uncus
Heschl’s gyrus/gyri
(transverse temporal gyrii, Brodmann’s areas 41 and 42) - This is primary sensory cortex for audition.
Damage to Heschl’s
However, since information from both ears is processed bilaterally in the brain, damage to this area in only one hemisphere produces little deficit.
Damage to Heschl’s in both hemispheres results in
an inability to understand spoken language since auditory information is cut off from Wernicke’s area.
Superior temporal gyrus -
It is associated with audition and the posterior portion and superior surface lying within the lateral sulcus, called the planum temporale, (posterior to Heschl’s gyrus) makes up part of Wernicke’s area in the dominant hemisphere (for understanding langua
Planum Temporale
the posterior portion and superior surface (of the superior temporal gyrus) lying within the lateral sulcus, called the planum temporale, (posterior to Heschl’s gyrus) makes up part of Wernicke’s area in the dominant hemisphere (for understanding language
Middle, inferior, and occipito-temporal (fusiform) gyri
They are associated primarily with vision, particularly related to visual memory and perception.
bilateral lesions of the inferior temporal lobe
limited primarily to the fusiform gyri, results in prosopagnosia - an inability to identify or recognize faces).
Parahippocampal gyrus and uncus
The medial surface of the temporal lobe has a special association with memory.
Bilateral damage to parahippocampal gyrus and uncus
can lead to severe amnesia.
Anterior Commisure
The anterior parts of the temporal lobes and olfactory lobes (regions receiving terminations of the olfactory tract including the uncus, anterior part of the parahippocampal gyrus, and subcallosal gyrus) are interconnected via the anterior commissure
Frontal Lobe:
- Precentral gyrus 2. Superior and middle frontal gyri (posterior portions) 3. Inferior frontal gyrus (posterior portion) 4. Prefrontal cortex (rostral portions of the superior, middle and inferior frontal gyri)
- Precentral gyrus
This gyrus is called “primary motor cortex” or area 4 of Brodmann, and is a major source of axons that extend to the spinal cord (and other “motor areas”) for the control of voluntary movements.
Damage to the precentral gyrus
area results in weakness (paresis) and movement deficits on the opposite side of the body.
What helps to localize the damaged portion of the precentral gyrus?
because of the topographic localization of motor information within this gyrus to different parts of the opposite side of the body, specific motor loss helps to localize the damaged portion of this gyrus.
Superior and middle frontal gyri (posterior portions) -
This region includes “secondary motor” and “premotor” areas that also contribute to the organization of voluntary movements, including eye movements (frontal eye fields).
Damage to the Superior and middle frontal gyri (posterior portions)
can also result in forms of apraxia. If the damage is in the dominant hemisphere, the ability to write may be impaired.
If damage to the Superior and middle frontal gyri (posterior portions) is in the dominant hemisphere, what is the result?
Patients ability to write may be compromised
Inferior frontal gyrus (posterior portion) in the dominant hemisphere =
“Broca’s Area”
Broca’s Area is needed for?
the programming of speech and writing.
Damage to Broca’s Area
If it is damaged, patients lose the ability to generate fluent speech (although they can usually understand verbal or written statements).
If Broca’s is damaged why do patients have trouble understanding statements?
(Trick) Usually they CAN understand (Wernicke’s function) verbal or written statements
Prefrontal cortex
rostral portions of the superior, middle and inferior frontal gyri
Prefrontal cortex in humans
This region is far more developed in humans than in any other species.
What are the functions of the prefrontal cortex?
It’s difficult to delineate but many contribute to the make-up of a person’s personality. Others are associated with the planning and sequencing of complex tasks
Damage to the prefrontal cortex can lead to what?
personality changes that may be subtle or profound. In addition, patients sometimes develop compulsive, repetitive behaviors (related to their impaired ability to plan complex behaviors).
How are the frontal lobes interconnected?
via the genu of the corpus callosum.
Language functions are centered largely in the
dominant (left) hemisphere and involve more than one lobe.
How does information about speech enter the temporal cortex?
in Heschl’s gyrus and then spreads to Wernicke’s area which includes posterior portions of the superior temporal gyrus and the supramarginal gyrus.
Visual information from the occipital lobe that is related to reading enters what area and how does it do this?
Wernicke’s area via the angular gyrus
What happens to visual information after the it is passed through the angular gyrus?
language information is relayed to the frontal lobe
Broca’s area is in the
inferior frontal gyrus, where the commands for speech are organized.
“Wernicke’s aphasia”
(receptive or sensory aphasia) involves an inability to understand language and to speak coherently. In most cases it is associated with damage to Wernicke’s area.
“Broca’s aphasia”
(expressive or motor aphasia) is associated with an impaired ability to generate speech (or writing) and usually involves damage to Broca’s area.
CNS circulation has two major origins, what are they?
Vertebral Arteries and Internal Carotid Arteries
Where does the posterior circulation arise from?
the Vertebral Arteries
What are the vertebral arteries branches of?
they are branches of the subclavian arteries.
Where does the anterior circulation arise from?
the Internal Carotid Arteries.
What does the Posterior Communicating Arteries provide?
anastomoses between the two circulations. They may allow one circulation to perfuse the other if the latter occludes gradually from arterial disease.
How does the posterior communicating artery protect the brain during a sudden stroke?
However, because the Posterior Communicating Arteries are often small, the anastomoses will not protect the brain from a sudden stroke in one of the two circulations.
What does the posterior circulation supply?
the brainstem, cerebellum, and part of the cerebral cortex.
In the posterior circulation, what gives rise to small arteries?
spinal arteries that travel down the spinal cord.
What gives rise to the spinal arteries?
Vertebral arteries
What are the spinal arteries that the vertebral arteries give rise to?
two Posterior Spinal Arteries and one Anterior Spinal Artery.
What is the path of the spinal arteries and what reinforces their blood supply?
These arteries travel the length of the spinal cord and are reinforced by segmental branches from the Aorta.
As the Vertebral Arteries extend along the base of the medulla, what happens?
each gives rise to many medial and lateral branches that penetrate the medulla.
In addition to the medial and lateral branches that penetrate the medulla, what else happens to the vertebral arteries as it passes of the medulla?
They also produce prominent branches that supply the dorsolateral medulla and medial portions of the cerebellum (including the cerebellar nuclei). (PICA)
Posterior Inferior Cerebellar Arteries.
prominent branches that supply the dorsolateral medulla and medial portions of the cerebellum (including the cerebellar nuclei)
Where do the vertebral arteries join to form the Basilar arteries?
Near the junction of the medulla and the pons the Vertebral Arteries join to form the Basilar Artery.
What is the first branch of the basilar artery?
1) Anterior inferior cerebellar artery 2)
What is the location of the first branch off the Basilar Artery?
At or just beyond the junction of the medulla and pons
What does the first branch of the Basilar Artery supply?
a pair of branches (AICA) which supply the undersurface of the cerebellar cortex and central areas of the pontine tegmentum
What comes off the Basilar after AICA?
The basilar then gives off several small Pontine Arteries,
What does the pontine arteries supply?
the medial and lateral portions of the pons.
At the rostral end of the pons what large arteries arise off of the Basilar?
two more large branches, the Superior Cerebellar Arteries arise
What do the Superior Cerebellar Arteries supply?
the superior surface of the cerebellar cortex and dorsolateral areas of the pontine tegmentum.
At the rostral end of the Basilar Artery, what do those perforating branches contribute to?
the blood supply of the crus cerebri, posterior thalamus, and midbrain
What does the Basilar Artery bifurcate into?
the Posterior Cerebral Arteries
What is the path of the posterior cerebellar arteries?
travel along the medial surfaces of the temporal and occipital lobes. They also send branches to the midbrain, posterior parts of the thalamus and internal capsule (called Posterior Choroidal Arteries).
Each Posterior Cerebral Artery gives rise to what?
a branch that connects the posterior circulation with the anterior.
What is the connection between the posterior and anterior circulation?
Posterior communicating artery
What is the function of the Posterior Communicating Artery perforating branches?
They give rise to important perforating branches to the thalamus, midbrain, and crus cerebri.
What does the anterior circulation arise from?
the Internal Carotids.
What is the first branch off of the internal carotids?
As each of these large arteries enters the skull, it sends a branch that follows the optic nerve into the orbit, the Ophthalmic Artery.
As the carotids continue into the skull at what level does it meet the PCA?
At the level of the optic chiasm.
After the PCA connects to the ICA, what are the two major branches that it gives off, and what does it supply?
two major branches that supply the surface of the cerebral cortex, the Anterior Cerebral Artery and the Middle Cerebral Artery.
Each Anterior Cerebral supplies what?
the medial surface of the frontal and parietal lobes in one hemisphere
Each Middle Cerebral supplies what?
the most of the lateral surface of one cerebral hemisphere including the insula
Where does the anterior choroidal artery arise from?
arising at the junction between the PCA and ICA (sometimes off the Posterior Communicating Artery)
What is the path of the Anterior Choroidal Artery?
runs posteriorly and then penetrates deep into the brain
What does the anterior choroidal artery supply?
It supplies the anterior part of the choroid plexus and hippocampus, and continues superiorly to supply areas of the brain near more posterior parts of the internal capsule.
A series of small branches (end arteries) that arise from the proximal portion of the Middle Cerebral Artery, what structures do these supply?
the basal ganglia and parts of the internal capsule. (lenticulostriate arteries)
Lenticulostriate Arteries
A series of small branches (end arteries) that arise from the proximal portion of the Middle Cerebral Artery that supplies the basal ganglia and parts of the internal capsule
The two Anterior Cerebral Arteries are joined by the
Anterior Communicating Artery, thus completing the arterial circle known as the Circle of Willis
Venous blood from the cerebral cortex is collected mainly into what?
the superficial cerebral veins,
What do the superficial cerebral veins drain into?
it drains into all of the dural sinuses
Deep structures of the cerebrum drain largely into what structure?
the great cerebral vein (of Galen)
What does the great cerebral vein of Galen drain into?
the straight sinus.
Most of the blood from the dural sinuses drain into what?
the internal jugular vein which begins at the base of the skull
In addition to the internal jugular vein, what else does the dural sinuses drain into?
there are significant drainage pathways to the facial veins, basilar venous plexus to the vertebral venous plexus and through the cavernous sinus to the pterygoid plexus and maxillary veins.
What is the distribution of the anterior spinal artery?
1) ventral 2/3 of the spinal cord 2) medial medulla
What are the major symptoms associated with the branch of the anterior spinal artery in the spinal cord?
Paralysis, loss of pain and temperature sense below occlusion
What are the major symptoms associated with the branch of the anterior spinal artery in the medial medulla?
Contralateral sensory loss and paresis, ipsilateral tongue paralysis
What is the distribution for the posterior inferior cerebellar artery?
Dorsolateral medulla and pons, medial cerebellum, cerebellar cortex
What are the major symptoms associated with posterior inferior cerebellar artery?
Wallenburg’s syndrome: vertigo, loss of balance, ipsilateral cerebellar signs, loss of facial pain sensation, hoarseness
What is the distribution for the anterior inferior cerebellar artery?
inferior surface of cerebellar cortex, dorsolateral pons
What are the major symptoms associated with anterior inferior cerebellar artery?
ipsilateral “cerebellar signs” (tremor, ataxia), facial paralysis, ipsilateral hearing loss, loss of pain and temperature over face ipsilaterally
What is the distribution for the basilar branches?
pons, anterior midbrain (crus cerebri)
What are the major symptoms associated with basilar branches?
paralysis and loss of sensation in the face, body and limbs; can also affect eye movements and cause diplopia
What is the distribution for the superior cerebellar arteries?
superior surface of cerebellum, dorsolateral corner of rostral pons
What are the major symptoms associated with superior cerebellar arteries?
ipsilateral cerebellar signs, contralateral pain and temperature loss, Horner’s
What is the distribution for the posterior cerebral arteries?
occipital lobe, medial portions of parietal and temporal lobes, anterior & posterior midbrain, crus cerebri, posterior thalamus
What are the major symptoms associated with posterior cerebral arteries?
if unilateral: blindness in the visual field contralateral to the affected side, alexia (left side). if bilateral as with “top of the basilar” occlusion: bilateral blindness, memory loss, somatosensory loss, coma & death
What is the distribution for the posterior communicating branches?
anterior midbrain, crus cerebri, thalamus
What are the major symptoms associated with posterior communicating branches?
contralateral paresis, coma & death
What is the distribution for the middle cerebral arteries?
Lateral surface of cortex, insula
What are the major symptoms associated with middle cerebral arteries?
deficits can include – contralateral paralysis and sensory loss; “apraxia”; aphasia; partial blindness
What is the distribution for the anterior cerebral arteries?
medial surface of parietal and frontal lobes
What are the major symptoms associated with anterior cerebral arteries?
contralateral paralysis and sensory loss in leg and foot; sometimes, apraxia
What is the distribution for the lenticulostriate arteries?
Basal ganglia, amygdala, internal capsule, anterior thalamus
What are the major symptoms associated with lenticulostriate arteries?
Possibly, involuntary movements (basal ganglia); paralysis, sensory deficits over the entire ½ of the body, homonymous visual field deficits. (internal capsule)
What is the distribution for the anterior choroidal arteries?
hippocampus, anterior choroid plexus, posterior internal capsule
What are the major symptoms associated with the anterior choroidal arteries?
With hemorrhage may cause paralysis, sensory deficits, visual field defect (internal capsule)
