7. Stroke

Question 1

O. Describe the basic anatomy and function of the brain, including the following:
oFrontal lobe, including Broca’s area
oTemporal lobe, including Wernicke’s area
oParietal lobe
oOccipital lobe
oCerebellum
oBrain stem (midbrain, pons, medulla-location of cranial nerves)

visual???

Answer 1

Frontal – contains Broca’s area (expressive dysphasia if lost), usually on the left. Contains pre- central gyrus for motor and contains prefrontal cortex, a lot of your personality
Temporal – contains Wernicke’s area (receptive dysphasia if lost), usually on the left in the superior temporal gyrus, primary auditory cortex. Temporal lobe curls round to form the hippocampus.
Parietal – somatosensory cortex
Occipital – primary visual cortex, calcarine sulcus
Association cortexes – involved in all the other cortexes, brings everything together/refines the sensation
In visual – lateral geniculate goes straight to calcarine sulcus, superior colliculi go to the visual association cortex
Cerebellum
In the posterior cranial fossa

Question 2

Strokes:

Middle cerebral artery

Anterior choroidal branch

Posterior cerebral artery

Answer 2

1. Middle cerebral artery – loss of motor function (apart from in the leg), Broca’s and Wernicke’s
   areas, choroidal branch supplies the internal capsule, part of the calcarine sulcus (macula sparing in a posterior cerebral artery stroke)
2. Anterior cerebral artery – loss of motor function of the leg, supplies caudate nucleus, internal capsule, cingulate gyrus (inappropriate emotional response), branches to the corpus callosum, olfactory tract and bulb (so you may have dysnosmia)
3. Posterior cerebral artery – supplies most of the calcarine sulcus apart from a small bit which is supplied by the middle cerebral artery (macula sparing). Provides some of the supply to the thalamus.

Question 3

O. Cerebellum cont.

Answer 3

In the posterior cranial fossa
Cerebellum = roof of the 4th ventricle, (the floor is the posterior aspect of the brainstem – rhomboid fossa), the lateral walls are formed by the cerebellar peduncles
Convoluted surface = folia
Primary fissure = separates anterior and posterior lobes
Midline vermis
Posterolateral fissure on the underside = marks the flocculonodular lobe
Superior cerebellar peduncle conveys they spinocerebellar tract – connecting the cerebellum to the midbrain
Middle – cortciopontocerebellar tract (cortex – pons – cerebellum)
Inferior peduncle – conveys the vestibulocerebellar tract and the dorsal spinal cerebellar tract (connects cerebellum to medulla oblongata)
Flocculus – lies just under the cerebellar peduncles, lies immediately below entry point of vestibulocochlear nerve. Role of floccus = associated with the vestibulo-occular system
Nuclei of the cerebellum:
External grey matter, internal white matter (contains the deep cerebellar nuclei)
Arba vitae – white matter projections
Outer layer = fibre rich molecular layer
Intermediate layer = Purkinje cell layer
Inner layer = granule layer with granule cells
Fibres from the cerebellum project to the cortex as either mossy or climbing fibres
Mossy fibres synapse with the granule cells and bifurcate to form parallel fibres
Purkinje cells use GABA as their neurotransmitter – so the OUTPUT OF THE CEREBELLUM IS TOTALLY REGULATED BY INHIBITORY NEURONES (GABA is an inhibitory neurotransmitter)
Deep cerebellar nuclei:
1. Dentate nucleus – responsible for planning, initiation and control of voluntary movements
2. Fastigial nucleus
3. Globose
4. Emboliform
Ascending fibres of the cerebellum
Mossy fibres relay sensory information to the granule cells
Granule cells project along parallel fibres to reach the Purkinje cells
The purkinje cells is where it all gets processed and stimulates a descending motor response
Climbing fibres – ascend from the inferior olivary nucleus (involved in sound) to the cerebellum. Another ascending pathway into the cerebellum.
Functional areas of the cerebellum
Archicerebellum Made up of flocculonodular lobe & fastigial nucleus – maintenance of
balance
Paleocerebellum
Cerebellar legions –
Vermis: loss of ipsilateral muscle tone and posture
Stroke to cerebellum – loss of balance and visual disturbance
Sharkot’s triad = intention tremor + nystagmus + dysarthria (difficulty speaking caused by problems controlling the muscles used in speech)
Other lesion – spinal cord lesion of the anterior white commissure causes bilateral symptoms

Question 4

deep cerebellar nuclei

Answer 4

Deep cerebellar nuclei:

1. Dentate nucleus – responsible for planning, initiation and control of voluntary movements
2. Fastigial nucleus
3. Globose
4. Emboliform

Question 5

O. Describe the difference between upper motor neurone lesion and lower motor neurone lesions

Answer 5

Upper motor neurones = from the cortex to the spinal cord
Made up of midline vermis and surrounding paravermis, also including the globose and emboliform nuclei – influences muscle tone and posture
Neocerebellum The majority of the cerebellum, involves the dentate nucleus – involved in
muscle coordination, trajectory, speed and force of movement. The mossy fibres originate from the pontine nucleus and are involved in the planning and execution of movement, and enter via the middle cerebellar peduncle.
Lower motor neurones = neurones that connect the impulse from the spinal cord to the effector muscle
Upper motor neurones Lower motor neurones
Muscle weakness Muscle weakness
Little/no wasting/atrophy Muscle wasting atrophy
No fasciculations Fasciculations
Hyperreflexia Hyporeflexia
Increased tone (spasticity) Decreased tone (flaccidity)
Positive Babinski reflex No Babinski reflexes
Upper motor neurone lesions = cause Hyperreflexia because they have no inhibitory action on the lower motor neurones
Vascular damage – rapid onset of symptoms
Trouble chewing & fine muscle trouble = myasthenia gravis (NMJ troubles)

Question 6

Corticospinal tract

Answer 6

white matter motor pathway starting at the cerebral cortex that terminates on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk.
Arises from Betz cell bodies in the primary motor cortex
Passes down from the cortex through the corona radiata
Then passes through the internal capsule
Pass down to the brainstem
Pass through the crus cerebri of the midbrain (peduncle)
75-90% decussate at the medullary pyramids – these decussated fibres supply the limbs
The 10-25% non-descended fibres go on to supply the trunk (axial fibres)
Decussated fibres desecend in the lateral corticospinal tract, non-decussated fibres descend in the anterior corticospinal tract
When the axial fibres are ready to decussate, they cross at the anterior white commissure at the level they want to leave the spine
The lateral corticospinal tract descends and leaves the spine, first synapsing at anterior horn cells
Fibres then project from the anterior horn cells as lower motor neurones to innervate the muscle