2020 - 10 - 29 - Εγκεφαλικά Ημισφαίρια και Αγγειακά Σύνδρομα - Μήτσιας
2020 - 10 - 29 - Εγκεφαλικά Ημισφαίρια και Αγγειακά Σύνδρομα - Μήτσιας
2020 - 10 - 29 - Εγκεφαλικά Ημισφαίρια και Αγγειακά Σύνδρομα - Μήτσιας
Αγγειακά Σύνδρομα
ΠΑΝΑΓΙΩΤΗΣ ΜΗΤΣΙΑΣ
ΚΑΘΗΓΗΤΗΣ ΝΕΥΡΟΛΟΓΙΑΣ, ΙΑΤΡΙΚΗ ΣΧΟΛΗ, ΠΚ
ΔΙΕΥΘΥΝΤΗΣ ΝΕΥΡΟΛΟΓΙΚΗΣ ΚΛΙΝΙΚΗΣ ΠΑΓΝΗ
Cortical Regions (Φλοιϊκές Περιοχές)
o Primary motor cortex (πρωτεύων κινητικός φλοιός)
… precentral gyrus of the frontal lobe
Knowing the locations of the motor cortex and these three primary sensory cortices allows for a
logical deduction o the functions of the rest of the cortical surface
Dominant vs. Non-dominant Hemisphere
Επικρατητικό - Μη-επικρατητικό Ημισφαίριο)
o The hemisphere contralateral to the side of handedness is considered the dominant
hemisphere
₋ e.g., the left hemisphere in a right-handed patient
o Most patients are right-handed, so their left hemisphere is the dominant hemisphere
o Language dysfunction (διαταραχή λόγου) is most commonly due to lesions in the dominant
(usually left) hemisphere
o Neglect (αμέλεια) is most commonly due to lesions in the non-dominant (usually right)
hemisphere (causing left-sided neglect)
Parietal Lobes – Sensation
Βρεγματικοί Λοβοί - Αισθητικότητα
Primary Sensory Modalities
− Pain and Temperature
− Pallesthesia (παλλαισθησία)
− Joint position sense (θέση μελών στο
χώρο-ιδιοδεκτικότητα)
• Although these terms are commonly confused, their names provide clues to what they signify:
₋ kinetic is difficulty with movements themselves
₋ ideational is loss of the idea of how to perform an action
₋ ideomotor is difficulty translating an idea into a motor plan.
₋ The latter two types of apraxia are generally caused by lesions of the parietal lobe in the dominant (usually
left) hemisphere
Temporal Lobes (κροταφικοί λοβοί):
Recognition Memory (μνήμη αναγνώρισης)
▪ The temporal lobes are ideally located to combine sensory input from olfactory, auditory,
visual, and somatosensory cortices.
▪ The temporal lobes are thus ideally suited to play a role in recognition memory, since
memories are internal representations o sensory experiences. Lesions o the medial temporal
lobes (including the hippocampus) can cause amnesia
▪ The flow of visual information inferiorly to the temporal lobe (the ventral stream) is referred
to as the “what pathway:”
▪ Visual information is processed here to determine what things are (recognition memory).
▪ The dominant (usually left ) inferior temporal lobe houses the visual word form area
necessary for reading, and the nondominant (usually right) inferior temporal lobe houses the
face recognition area.
▪ Inability to read is called alexia and inability to recognize aces is referred to as prosopagnosia.
Fontal Lobes – Motor
Μετωπιαίοι Λοβοί - Κίνηση
Frontal Lobe
Horizontal Gaze (οριζόντιο βλέμμα)
➢ Lesions in and around Broca’s and Wernicke’s areas lead to speech disturbances (aphasia).
Αφασία (Διαταραχή Λόγου)
Aphasias (Language Deficit)
Aphasias are language deficits
Note
• All of the transcortical aphasias are characterized by preserved repetition, and named for the
primary language deficit:
• transcortical motor aphasia is characterized by a deficit in speech production (motor output)
• transcortical sensory aphasia is characterized by a deficit in speech comprehension (“sensation” of speech)
• mixed transcortical aphasia is characterized by a mix of both expressive and receptive aphasia
Conduction aphasia (αφασία αγωγής)
• If a patient’s only language deficit is repetition with preserved comprehension and production
• Conduction between Wernicke’s area and Broca’s area (via the arcuate fasciculus) is disrupted.
o Four basic types of circuitry pass through thalamic nuclei en route to the cortex:
Thalamic Circuitry (θαλαμικά κυκλώματα)
1. Sensory pathways.
÷ All sensory pathways synapse in the thalamus, which transmits sensory in formation to the respective
sensory cortices.
÷ Smell is the only sensory modality that reaches the cortex before the thalamus (transmitted directly to the
olfactory cortex, which then transmits smell in formation to the thalamus (dorsomedial nucleus)
2. Motor control pathways.
÷ The ventral anterior (VA) and ventral lateral (VL) nuclei of the thalamus participate in cortical–basal
ganglia–cortical loops and cerebellar–cortical pathways
3. Consciousness/arousal pathways.
÷ These pathways begin in the brainstem reticular activating system and project to both thalami, which in
turn project diffusely throughout the cortex
4. Cognition/emotion pathways.
÷ Corticocortical loops pass through the thalamus, playing roles in diverse cognitive functions.
÷ The circuit of Papez which participates in memory and emotion: hippocampus→ fornix→mamillary
bodies→anterior nucleus of the thalamus→anterior cingulate→entorhinal cortex→hippocampus.
➢ Individual thalamic nuclei can be affected by small strokes
• e.g., lacunar stroke in ventral posterior medial/ventral posterior lateral [VPM/VPL] thalamic nuclei causing contralateral sensory
loss
➢ Given its diffuse connections with diverse cortical regions, lesions of the thalamus are said to
be able to “do anything” (i.e., cause any type of deficit), including causing “cortical” signs (e.g.,
aphasia, neglect, cognitive deficits) and eye movement abnormalities (in part due to effects on
nearby midbrain pathways or eye movements).
The Basal Ganglia (Βασικά Γάγγλια)
• The basal ganglia include the caudate (κερκοφόρος πυρήνας), putamen (κέλυφος), globus
pallidus (ωχρά σφαίρα), and subthalamic nucleus (υποθαλάμιος πυρήνας)
• The caudate and putamen together are referred to as the striatum (ραβδωτό σώμα)
• The putamen and globus pallidus together are referred to as the lenticular nuclei (φακοειδής
πυρήνας).
• The basal ganglia are part of circuits that initiate and coordinate movements
• Dysfunction in the basal ganglia leads to movement disorders (e.g., Parkinson’s disease)
• When the basal ganglia are affected by cerebrovascular disease, the surrounding internal
capsule (έσω κάψα) is also often affected, causing the predominant manifestation to be
contralateral weakness, with movement disorders being relatively uncommon in this scenario.
• One exception is stroke o the subthalamic nucleus, which can produce contralateral hemiballismus
(unilateral ballistic movements).
• Slower growing lesions involving the basal ganglia (e.g., tumors, toxoplasmosis) can cause
contralateral movement disorders
Arterial Supply of the Cerebral
Hemispheres
➢ The brain, brainstem, and cerebellum are supplied by arteries
arising from:
… the paired internal carotid arteries (the anterior circulation)
… the paired vertebral arteries (the posterior circulation)
➢ The internal carotid arteries arise from the common carotid
arteries, which themselves arise from the aortic arch (from the
brachiocephalic trunk on the right and directly from the aortic arch
on the left)
➢ Each carotid artery ultimately gives rise to:
… middle cerebral artery (MCA)
… anterior cerebral artery (ACA)
… these arteries together supply the majority o the cerebral hemispheres
including the frontal lobes, parietal lobes, and superior and lateral
temporal lobes
➢ Each internal carotid artery also gives rise to:
… ophthalmic artery (which supplies the retina)
… anterior choroidal artery (which supplies the posterior thalamus and
internal capsule)
➢ The vertebral arteries arise from the subclavian arteries, join to form the basilar artery at
around the level of the pontomedullary junction, and end by giving o the posterior cerebral
arteries (PCAs) at the level of the upper midbrain
➢ The PCAs supply the regions o the cerebral hemispheres not supplied by the MCAs and ACAs:
• occipital lobes
• inferior and medial temporal lobes.
➢ Before giving rise to the PCAs, the vertebrobasilar system gives to three paired circumferential
arteries that supply the lateral brainstem and cerebellum
• superior cerebellar arteries [SCAs]
• anterior inferior cerebellar arteries [AICAs]
• posterior inferior cerebellar arteries [PICAs]
o The anterior circulation and posterior circulation are linked by the posterior communicating
arteries
o The ACAs are linked by the anterior communicating artery.
o These connections form the circle of Willis on the inferior surface of the brain, which provides
routes or collateral flow.
o Not all patients have a complete circle of Willis, and some patients have anatomic variants
Magnetic Resonance Angiography
CT Angiography
Anatomic variants of intracranial vessels
❑ Hypoplastic vertebral artery.
▪ Many patients have one dominant vertebral artery and a smaller hypoplastic nondominant vertebral artery.
▪ When this occurs, the basilar artery appears to swing to the side o the nondominant vertebral artery, and
the vertebral canal is smaller on the side o the congenitally smaller vertebral artery. These features help to
distinguish a congenitally smaller vertebral artery from a pathologically smaller one (e.g., due to dissection
or atherosclerosis).
❑ Azygous ACA:
▪ both ACAs emerge from a common trunk
❑ Fetal PCA:
▪ the PCA arises from the internal carotid artery rather than the top o the basilar. This variant may occur
unilaterally or bilaterally
❑ Artery of Percheron:
▪ a single artery from one o the PCAs supplies both thalami (rather than an individual supply on each side).
The Vascular Territories of the ACA, MCA, and PCA
o Most generally, the ACAs and MCAs supply the anterior, medial, and lateral aspects o the
hemispheres, and the PCAs supply the posterior and inferior aspects.
o On the cortical surface:
o the MCAs supply the lateral surface of the frontal, temporal, and parietal lobes
o the ACAs supply the medial surface o the frontal and parietal lobes
o the PCAs supply the occipital lobes and the inferior temporal lobes.
o Extending subcortically:
o the MCAs supply the majority of the hemispheres, creating a trapezoidal shape in the axial plane—
anteriorly
o medially to this trapezoid are supplied by the ACAs
o posteriorly and inferiorly are supplied by the PCAs (including the thalamus, which is supplied by
penetrating vessels arising rom the PCAs and posterior communicating arteries).
Watershed (Borderzone) Territories
❖ The watershed (borderzone) territories are the regions at the border of two arterial territories.
❖ The MCA-ACA and MCA-PCA borderzones are the most commonly discussed borderzones
❖ There is also a borderzone between AICA and PICA, as well as a deep borderzone territory
between the lenticulostriate branches o the MCA (penetrating rom below) and the
leptomeningeal branches of the MCA (penetrating from above).
▪ Although the common teaching is that borderzone infarction is due to hypoperfusion, borderzone
strokes can also be caused by emboli: the smallest possible emboli travel as distally as possible before
causing an occlusion, they will arrive at the end-arterial territories, which are the borderzones.
❖ So although borderzone infarction can certainly be due to hypoperfusion, this is not always the
cause, and an embolic etiology should also be considered as the etiology of borderzone
infarction
Clinical Syndromes Associated With Cerebral
Vascular Territories
Any artery or arterial branch may be affected by ischemic stroke, with corresponding symptoms
related to the location and size o the infarct.
• Ataxic-hemiparesis:
unilateral hemiparesis/hemiplegia (due to involvement o the corticospinal tract) with ataxia in the weak limb(s) due to
interruption o the corticopontocerebellar fibers destined or the middle cerebellar peduncles
this can occur due to lacunar stroke in either the internal capsule or the anterior pons, both of which are places where
the corticospinal tract and corticopontocerebellar fibers run together
• Dysarthria–clumsy hand:
dysarthria and unilateral upper limb ataxia
localization is the same as or ataxia-hemiparesis (internal capsule or anterior pons).
Pure Motor Stroke Pure Sensory Stroke Ataxic Hemiparesis
Posterior Limb of Internal Capsule Thalamus Basis Pontis
Infarction in the Watershed
(Borderzone) Territories
o The MCA-ACA watershed regions span the “stripes” at
the border o the two territories.
o Τhe part of the motor homunculus supplied by the MCA-
ACA watershed region includes the proximal arm and leg,
which are joined at the shoulder and hip in the
homunculus.
o Infarction in the MCA-ACA borderzone can cause
proximal arm and leg weakness with preserved strength
distally in the hands and feet.
• When this occurs bilaterally, it causes what is called the “person in a
barrel” syndrome since the distal arms and legs function well but the
proximal limbs are weak (simulating a person in a barrel with the hands and
feet sticking out).
The MCA-PCA watershed region is at the
parietooccipital junction.
When the MCA-PCA watershed region is affected
bilaterally, the patient will often have deficits in
visual attention that can include some or all of the
elements of Balint’s syndrome:
◦ optic ataxia,
◦ ocular apraxia,
◦ simultanagnosia