GEP (Life control) Week 3 Flashcards
What are the 3 main movement pathways
- Corticospinal (pyramidal) tract:
Carries the messages from brain to peripheral nervous system
Damage = weakness (paresis) or full paralysis - Extrapyramidal system (basal ganglia):
Acts as a checkpoint to begin voluntary movement
Modulates speed and smoothness of movement
Underactivity = slow movement (bradykinesia), muscle rigidity, difficulty initiating movement
Overactivity = uncontrolled involuntary movements - Cerebellum:
Coordinates movements in space + learned motor patterns
What is the 3 main components of the brain
Cerebrum, Cerebellum and Brain stem
Identify the cranial fossass
What are the main 3 arteries that supply the cerebral cortex
Anterior, middle and posterior cerebral arteries -> form the Circle of Willis
Anterior circulation from internal carotid arteries:
Anterior cerebral artery
Middle cerebral artery
Posterior circulation from vertebral arteries
Posterior cerebral artery
* + cerebellum + brainstem
Describe the way that the Aneterior, middle and posterior cerebral arteries arise
Anterior circulation
Internal carotid passes through carotid canal
Loops back on itself then becomes the MCA
The ACA bificates of the MCA
Posterior circulation
Vertebral arteries pass through foramen magnum then come together to form basilar artery
Basilar artery works its way up the front of the brainstem (I’ll cover its other branches later)
Basilar eventually gives off the PCA which loops round to the back of the cerebrum
What are the territories within the cerebral cortex that each of the 3 main cerebral arteries supply
This is just a different view of the cerebral artery regions
the boarders of the cerebral arteries are not the same as the borders of the lobes in the brain
The MCA and PCA supplies which lobe of the brain that receives input from the macula (central vision)
The temporal lobe
What are the structures and functions of the cerebellum
- Cerebellum is responsible for coordination in space as well as learned motor patterns
- Middle of the cerebellum (vermis) handles coordination of the trunk and proximal muscles: important for posture (damage = truncal ataxia)
- More lateral parts = coordination of the peripheries (damage = limb ataxia)
- Flocculonodular lobe – linked to the vestibular balance system in the ear (damage = vertigo, nausea)
- Unilateral cerebellar damage produces symptoms on the
- ipsilateral (same) side
What are the cerebeller pathology
The best way to remember is DDANISH
There cerebellum coordinates movement in space through proprioception and visual input
Dysdiadochokinesia - inability to perform rapid, alternating muscle movements (finger tapping, opening and closing of fists etc)
Dysmetria - inability to judge distance
-Past-pointing
-Cerebellar rebound produces overshoot
-Difficulty focusing eyes on target
Ataxia - clumsiness.
-Cerebellar gait - usteady on feet, legs wide apart, veering towards side of cerebellar lesion
-Lateral cerebellar damage: limb ataxia (may also produce cerebellar gait)
**Nystagmus **- jerking of eyes. Eyes try to drift back to midline then jerk back to target
Intention tremor - involuntary, rhythmic muscle contractions (oscillations) that occur during a purposeful, voluntary movement.
Staccato speech (dysarthria - trouble speaking)
Hypotonia – low levels of muscle tone
What is the doll’s eye reflex
Cerebellum and brainstem connect the vestibular (balance) system in the inner ear to the occulomotor nerves
This produces the vestibulo-ocular reflex:
Turning the head one way produces reflexive movement of the eyes in the other direction so your gaze stays fixed on target
Loss -> ‘doll’s eyes reflex’ – where eyes move with the head
Loss of the vestibulo-ocular reflex is one of the signs doctors look for when confirming brainstem death
VO reflex can also be lost without brainstem death (vertigo etc)
What is the blood supply to the cerebellum
Basilar artery
Vertebral arteries
Superior cerebellar artery (SCA)
Anterior inferior cerebellar artery (AICA)
Posterior inferior cerebellar artery (PICA)
What is the blood supply to the brainstem and midbrain
The midbrain, pons and medulla oblongata are supplied by lots of tiny branches from the basilar artery and PCA.
These perforating/penetrating vessels:
Have tiny diameter, so vulnerable to blockage
Branch off at right angles (never a good design choice) so vulnerable to haemorrhage/damage
Damage to these tiny perforating vessels produces ‘lacunar’ infarcts –tiny areas of necrosis that leave small holes in the midbrain/brainstem
Usually lots of these have to accumulate over time
to produce serious symptoms
Desribe the venous drainage of the brain
Cerebral veins:
They lack muscular walls and valves
Empty into dural venous sinuses
NB: The cerebral venous system doesn’t follow arteries!
What are the main dural venous sinuses
Think of venous blood flowing from all points towards the confluence of sinuses posteriorly, then round and down to the internal jugular vein
What is a cerebral venous sinus thrombosis
CVST is when a thrombus occludes one of the dural venous sinuses, leading to accumulation of deoxygenated blood within the brain parenchyma -> cytotoxic oedema
DVT of the brain
CSF is also not able to drain
0.5-3% of strokes
Clinical features: headache, nausea, vomiting and neurological defects.
What is intracranial hemorrhage/haematoma
A hemorrhage refers to ongoing bleeding while the blood in a hematoma has typically already clotted.
There are 4 main types:
epidural Haemotoma
Intracerebral Haemotoma
Subcranial Hemorrhage
Epidural Haemotoma
What is an extradural haemorrhage
-Lentiform/lemon shaped
-Lemon-shaped because the periosteal dura, which should be attached to the bone of the skull, is torn away by the pressure of the haemorrhage (so only goes so far).
Classically caused by a rupture of the middle meningeal artery due to a skull fracture at the pterion – a weak point over the temple
What is a subdural haemorrhage/Haemotoma
-Crescentic/banana shaped
-Banana shaped because blood can fill the subdural space all the way until it is stopped by the falx cerebri at the midline
-Venous blood rather than arterial
-Classically caused by rupture of the veins that pass from the brain into the subdural space
What is a subarachnoid haemorrhage
-Blood is between the arachnoid mater and pia mater, so closely follows the contours (gyri and sulci) of the cortex
-Most commonly due to a ruptured aneurysm in the Circle of Willis
-Dramatic onset
-“worst pain ever experienced”
-May cause meningism (photophobia, neck stiffness,
positive Kernig’s)
What is the circle of willis
The circle of Willis is an important junction of arteries at the base of the brain. The structure encircles the middle area of the brain, including the stalk of the pituitary gland and other important structures.
Two arteries, called the carotid arteries, supply blood to the brain. They run along either side of the neck and lead directly to the circle of Willis.
Each carotid artery branches into an internal and external carotid artery. The internal carotid artery then branches into the cerebral arteries. This structure allows all of the blood from the two internal carotid arteries to pass through the circle of Willis.
The structure of the circle of Willis includes:
left and right internal carotid arteries
left and right anterior cerebral arteries
left and right posterior cerebral arteries
left and right posterior communicating arteries
basilar artery
anterior communicating artery
Give a quick overview on the production and function of the cerebrospinal fluid
Functions of CSF:
Support, shock absorber, homeostasis (pressure, waste, temperature), nutrition, immune function
Production:
CSF is made by the choroid plexus, mainly in the walls of the lateral ventricles (also 3rd and 4th ventricles).
The choroid plexus consists of pia mater, fenestrated capillaries, and ependymal cells (which make the CSF!)
Approximately 500ml is produced every day.
What is the flow of CSF from the production to the subarachnoid space
Lateral Ventricle (x2) → Foramen of Monro (x2) → Third Ventricle → Cerebral Aqueduct → Fourth Ventricle
The CSF then enters the subarachnoid space via:
One of the two foramina of Luschka
→ cisterna magna → SA space
Foramen of Magendie
→ cerebellopontine cisterns → SA space
A small amount goes straight into the central canal of the spinal cord
How is CSF removed
CSF is absorbed by arachnoid villi/granulations mostly in the superior sagittal sinus, where the most arachnoid granulations are. It then enters the cerebral venous system, following a pressure gradient.
What occurs in the late stages of increased ICP after it is not treated
What is a great way to identify strokes
FAST:
Face
Arms
Speech
Time
What are the different types of stroke
Haemorrhagic Stroke (13%)
Rupture of a cerebral blood vessel (venous or arterial), typically due to weakness in the vessel wall. Classified according to site of bleeding.
Ischaemic Stroke (87%)
Reduced blood supply and subsequent hypoperfusion to tissues, mostly due to thrombus within the cerebral arteries (e.g. secondary to atherosclerosis) or from an embolism, leading to infarction. The vessel affected largely affects the range of symptoms a patient will have.
How is strokes classified and what are the classification
Bamford/Oxford Stroke Classification is used to classify strokes
Total Anterior Circulation Infarct (TACS)
Involvement of both the ACA and MCA of the affected side
Unilateral weakness (contralateral hemiplegia/hemiparesis) Homonymous hemianopia (contralateral)
Higher cerebral dysfunction (e.g. aphasia, visuospatial neglect)
Partial Anterior Circulation Infarct (PACS)
Involves either the ACA or MCA of the affected side. Two of the TACI symptoms (or higher cerebral dysfunction alone)
Lacunar Infarct (LACI)
Subcortical stroke secondary to small vessel disease. There is no loss of higher cerebral functions, but one of: Pure sensory/motor or sensorimotor stroke, or ataxic hemiparesis.
Posterior Circulation (POCS)
Cerebellar/Brainstem signs.
What is posterior stroke syndromes
These refer to sets of symptoms as a consequence of lesions in specific areas of the brainstem. This is more low-yield but get familiar with some of the names here.
What are examples of primary headache disorder
Migrane
Most common cause of chronic headache episodes
Usually unilateral pain
Lasts hours to days if untreated
Patient wants to lay down in dark, quiet room
20% are accompanied by aura (usually visual) which precedes pain
Followed by tired, ‘washed out’ feeling
Tension Headache
“Tight band” sensation
Pressure behind eye
More commonly bilateral
Cluster Headaches (trigeminal autonomic cephalagia)
Headache episodes are close together, often happening nightly for 1-2 months but then a long gap
Unilateral
Excruciating pain behind the eye Management:
Analgaesics don’t work
Subcut sumatriptan + high flow oxygen acutely
Verapamil, lithium or corticosteroids may terminate the current cluster
Other primary headaches:
“Ice pick” headache
Primary cough headache
Others e.g. on urination, orgasm etc
