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Questions and Answers

What structure is formed from the cells of the neural tube?

Schwann cells

Adrenal medulla

Motor neurons and glial cells (correct)

Melanocytes

Which lobe of the brain is primarily responsible for processing visual input?

Occipital lobe (correct)

Parietal lobe

Temporal lobe

Frontal lobe

What is the main function of the basal ganglia?

Language comprehension

Voluntary movement and habit formation (correct)

Regulation of body temperature

Emotional expression

Which sulcus separates the primary motor area from the primary sensory area in the brain?

Central sulcus Signup and view all the answers

Which part of the nervous system is comprised of the brain and spinal cord?

Central nervous system Signup and view all the answers

What is the role of Wernicke's area in the brain?

Language comprehension Signup and view all the answers

During which week of neurodevelopment does the neural tube begin to form?

Late Week 3 Signup and view all the answers

What does the insula primarily contribute to?

Emotion and behavior regulation Signup and view all the answers

Which structure is part of the limbic system and is involved in emotional processing?

Amygdala Signup and view all the answers

What do Schwann cells originate from?

Neural crest cells Signup and view all the answers

Which artery supplies the occipital lobe?

Posterior cerebral artery Signup and view all the answers

Which area of the frontal lobe is responsible for language production?

Broca’s area Signup and view all the answers

What is the main role of the cingulate gyrus in the brain?

Emotion regulation and memory Signup and view all the answers

Which part of the mesencephalon remains unchanged during development?

Mesencephalon Signup and view all the answers

What is the primary artery that supplies the lateral cerebrum?

Middle cerebral artery Signup and view all the answers

Which artery is formed by the convergence of the vertebral arteries?

Basilar artery Signup and view all the answers

What condition arises from the abnormal dilation of a vessel in the brain?

Aneurysm Signup and view all the answers

Which area is primarily supplied by the posterior cerebral artery?

Occipital lobe Signup and view all the answers

What is the most common type of stroke, accounting for 80% of cases?

Ischemic stroke Signup and view all the answers

Which of the following arteries branches from the vertebral artery?

Anterior inferior cerebellar artery Signup and view all the answers

During which type of stroke would one expect to see greater involvement of the legs than the arms?

Anterior cerebral artery stroke Signup and view all the answers

What significant role does the anterior communicating artery play in the Circle of Willis?

Joins anterior cerebral arteries Signup and view all the answers

What is a common clinical sign of a posterior cerebral artery stroke?

Amnesia Signup and view all the answers

What is the consequence of occlusion of the anterior spinal artery?

Medial medullary syndrome Signup and view all the answers

Which of the following best describes a common consequence of a lacunar stroke?

Contralateral pure motor loss Signup and view all the answers

What is the typical time frame for administering intravenous thrombolysis in acute ischemic stroke?

4.5 hours Signup and view all the answers

Which artery does NOT typically supply the cerebellum?

Basilar artery Signup and view all the answers

What is the primary function of the cerebrocerebellum?

Planning, modifying, and learning movements Signup and view all the answers

Which symptom is primarily associated with dysmetria?

Lack of coordination resulting in overshoot or undershoot Signup and view all the answers

Which of the following statements correctly represents the roles of the basal ganglia?

Shifts between mental sets and reinforcement learning Signup and view all the answers

What effect does the direct pathway of the basal ganglia have on the cortex?

Facilitatory effect promoting increased movement Signup and view all the answers

What is the role of dopamine in the basal ganglia pathways?

Selects between the direct and indirect pathways based on its presence Signup and view all the answers

What common symptom might indicate damage to the basal ganglia?

Hypokinetic disorders leading to over or under initiation of movements Signup and view all the answers

In the context of the indirect pathway, what is the main effect on the VLo?

Decreased excitatory effect on the cortex Signup and view all the answers

Which type of coordination issue is often characterized by slurred speech and intention tremor?

Ataxia Signup and view all the answers

Which anatomical feature is primarily affected in cerebrocerebellum pathology?

Lateral hemispheres Signup and view all the answers

What are common presentations related to cerebellar pathology?

Dysdiadochokinesia and ataxia Signup and view all the answers

How does the indirect pathway specifically affect the globus pallidus externus (GPe)?

Increases inhibitory effect on the subthalamic nucleus Signup and view all the answers

Which of the following is NOT associated with lesions in the cerebellum?

Overactive reflexes Signup and view all the answers

What is the primary function of the cerebellum-vermis?

Bodily posture and locomotion Signup and view all the answers

Which structure primarily carries information from the spinal cord to the cerebellum?

Inferior cerebellar peduncle Signup and view all the answers

What type of input does the flocculonodular lobe primarily receive?

Visual and vestibular input Signup and view all the answers

Which of the following is NOT a consequence of vestibulocerebellum lesions?

Ataxia Signup and view all the answers

What is the role of the dorsal column-medial lemniscal pathway?

To convey fine touch, vibration, and proprioception Signup and view all the answers

How do 2nd order neurons in the spinothalamic tract process sensory information?

They decussate immediately after synapsing with 1st order neurons Signup and view all the answers

Which descending tract is responsible for voluntary control of musculature?

Corticospinal tract Signup and view all the answers

The cuneocerebellar tract transmits proprioceptive information from which body part?

Upper limbs Signup and view all the answers

Which ascending tract is responsible for unconscious proprioception?

Spinocerebellar tracts Signup and view all the answers

Which tract carries information regarding pain and temperature sensations?

Lateral spinothalamic tract Signup and view all the answers

What complication can arise from herniation of the cerebellar tonsil?

Tonsillar herniation leading to brain stem compression Signup and view all the answers

What is the primary output of the superior cerebellar peduncle?

Motor output to the midbrain Signup and view all the answers

What function does the anterior spinothalamic tract serve?

Carries crude touch and pressure sensations Signup and view all the answers

What is the primary function of Broca's area?

Production of expressive language Signup and view all the answers

Which area of the brain is primarily involved in planning motor actions guided by memory?

Supplementary motor area Signup and view all the answers

Which cranial nerve is primarily responsible for the function of the inferior colliculus?

Cranial Nerve VIII Signup and view all the answers

Which brain structure is responsible for the modulation of sleep patterns?

Pineal gland Signup and view all the answers

In Lateral Medullary Syndrome, which of the following deficits is typically observed?

Contralateral alteration of pain and temperature Signup and view all the answers

Which area integrates sensory information to create an internal representation of the body?

Area 5 and 7 Signup and view all the answers

What characterizes Wernicke's aphasia?

Impaired comprehension of language Signup and view all the answers

What is the primary role of the cerebellum?

Coordinating and fine-tuning motor activity Signup and view all the answers

Which cranial nerves emerge from the medulla oblongata?

CN IX, CN X, CN XI, CN XII Signup and view all the answers

Which structure is known as the primary control center for descending pain modulation?

Periaqueductal gray Signup and view all the answers

Which area is primarily responsible for tactile sensation, such as touch and pressure?

Area 3 Signup and view all the answers

Which cranial nerve is responsible for the function of taste sensation in the anterior two-thirds of the tongue?

Cranial Nerve VII Signup and view all the answers

Which function is attributed to the inferior olivary nucleus?

Cerebellar motor learning Signup and view all the answers

Cranial nerves can be classified into which of the following categories?

Afferent vs. Efferent, Sympathetic vs. Somatic, General vs. Special Signup and view all the answers

Study Notes

The Nervous System

Responsible for signal transmission between body parts
Composed of the central nervous system (CNS) and peripheral nervous system (PNS)
CNS includes brain and spinal cord
PNS includes nerves and ganglia

The Brain

Composed of 3 primary vesicles: prosencephalon, mesencephalon, rhombencephalon
Prosencephalon
- Develops into the telencephalon (cerebrum) and diencephalon
- Telencephalon forms the cerebral cortex including frontal, parietal, temporal, and occipital lobes
- Telencephalon also forms subcortical structures including the basal ganglia, hippocampus, and amygdala
Mesencephalon remains the same and forms the midbrain
Rhombencephalon
- Develops into the metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata)

Brain Gyri and Sulci

Gyri are folds or ridges in the brain
Sulci are grooves or valleys in the brain
Key sulci include the central sulcus, pre-central sulcus, post-central sulcus, lateral sulcus (Sylvian fissure), parieto-occipital sulcus, orbital sulcus, and olfactory sulcus

The Frontal Lobe

Contains the primary motor cortex (pre-central gyrus)
Involved in voluntary movement and organisation of the motor homunculus
Contains the anterior association centre responsible for higher cognitive functions including planning, working memory, and speech
Also houses Broca's area which controls speech muscles and the olfactory area

The Parietal Lobe

Contains the primary somatosensory cortex (post-central gyrus)
Responsible for receiving sensory information (touch, pain, temperature)
Organisation of the sensory homunculus
Contains the somatosensory unimodal association cortex, angular gyrus, and supramarginal gyrus

The Temporal Lobe

Contains the primary auditory cortex
- Responsible for hearing
- Damage will cause deafness but reflexive reactions to sound persist
Contains the secondary auditory cortex
Involved in memory, language, and visual recognition
Contains Wernicke's area, which is responsible for comprehension of language

The Occipital Lobe

Contains the visual cortex
Responsible for receiving visual input, including colour, light, and movement
Supplied by the posterior and middle cerebral arteries

The Limbic Lobe

Located on the medial surface of each cerebral hemisphere
Involved in motivation, emotion, learning, and memory
Composed of the cingulate cortex, basal ganglia, amygdala, hippocampus, and thalamus

The Insula

Portion of the cerebral cortex folded deep within the lateral sulcus
Lies beneath the temporal, parietal, and frontal lobes
Part of the limbic system

Basal Ganglia

Group of subcortical nuclei at the base of the forebrain and top of the midbrain
Responsible for:
- Voluntary movement
- Habit
- Emotion
- Learning
Comprised of the lentiform nucleus (made up of the putamen and globus pallidus) and the caudate nucleus

Brodmann's Areas

Brodmann area 4 is the primary motor cortex (precentral gyrus) and is involved in simple movements.
Brodmann area 6 is the premotor area/supplementary area:
- PMA is involved in sensory-guided movements and control of proximal and trunk muscles.
- Proper SMA is involved in planning motor actions, especially those guided by memory.
- Pre-SMA is involved in acquiring new motor skills.
Area 3, 1, and 2 is the primary somatosensory cortex (post-central gyrus):
- Area 3 is involved in touch (nociception, light touch, and deep pressure).
- Area 1 is involved in texture.
- Area 2 is involved in size and shape.
Area 5 and 7 is the posterior parietal cortex:
- Integrates sensory information to create an internal representation of the body.
- Area 5 receives somatosensory information from the primary somatosensory cortex.
- Area 7 receives visual and proprioceptive information.
Area 17 is the primary visual cortex.
Area 44 and 45 is Broca's area.
Area 22, 29, and 40 is Wernicke's area.
Area 41 and 42 is the primary auditory cortex.

Brain Dominance

Brain dominance is determined by which side of the brain Wernicke's and Broca's areas are located.
Most people are left-brain dominant.
90% of right-handed people are left-brain dominant, while 50% of left-handed people are left-brain dominant.
This is significant in strokes as it can be used to identify whether there will be any speech impairment due to infarction of Broca's or Wernicke's area.

Aphasia

Aphasia is an impairment in language production or comprehension caused by neurological damage.
Broca's aphasia is also known as non-fluent aphasia or expressive aphasia:
- Decreased verbal expression.
- Speech perception is not affected.
- Language comprehension is normal.
Wernicke's aphasia is also known as deficits in comprehension of language or receptive aphasia:
- Fluent speech.
- Word salad.

Brainstem

Composed of the structures of the midbrain (mesencephalon) and hindbrain (rhombencephalon) and continuous with the spinal cord posteriorly.
Structures include:
- Midbrain.
- Medulla oblongata.
- Pons.
The cerebellum is a rhombencephalon structure, but not part of the brainstem.
Functions include:
- Cardiac and respiratory control.
- Regulation of circadian rhythms,
- Cranial nerve supply,
- Conveyance of motor and sensory pathways.

Midbrain

The pineal gland is a small endocrine gland part of the epithalamus that produces melatonin.
- Melatonin is a serotonin-derived hormone that affects the modulation of sleep patterns in seasonal and circadian rhythms.
The infundibulum connects the hypothalamus to the posterior pituitary gland.
The tectum is involved in visual and auditory reflexes.
- It sits on the dorsal aspect of the midbrain and is composed of the corpora quadrigemina.
- The superior colliculus (2) is the site of termination for 10% of visual afferent fibers and sends information to the lateral geniculate nucleus.
- The inferior colliculus (2) is the principle midbrain nucleus of the auditory pathway.
  - It receives input from the auditory cortex and peripheral brainstem nucleus.
  - It sends auditory information to the medial geniculate nucleus.
The cerebral aqueduct connects the third ventricle in the diencephalon to the fourth ventricle within the region of the medulla and pons.
The tegmentum is the portion of the midbrain ventral to the cerebral aqueduct.
- It communicates with the cerebellum via the superior cerebellar peduncles.
- It conducts various tracts, including the medial lemniscal pathway, spinothalamic tract, and rubrospinal tract.
The periaqueductal gray is the primary control center for descending pain modulation.
- It contains enkephalin-producing cells which suppress pain.
- It is located around the cerebral aqueduct within the tegmentum of the brain.
The substantia nigra is a subcortical structure involved in reward, addiction, and movement via dopamine.

Pons

A brainstem structure located inferior to the midbrain, superior to the medulla oblongata, and anterior to the cerebellum.
- It is separated from the midbrain and medulla oblongata via the inferior pontine sulcus and superior pontine sulcus, respectively.
Conducts motor and sensory signals via tracts.
Can be divided into ventral and dorsal pons.
Vasculature:
- The basilar artery runs down the midline of the ventral surface through the basilar groove.
- Largely supplied by pontine arteries - arising from the basilar artery, but also AICA and PICA.
Function: CN V-VIII functions, respiration, relaying signals.
Cerebral peduncles contain ascending and descending nerve tracts from the cerebrum to the pons.
- Occipito, parieto, temporo, frontopontine tracts.
- Corticospinal tract.
- Corticobulbar tract.
Essentially contains all structures of the midbrain except the tectum.
Cerebral crus is the anterior-most portion of the cerebral peduncle.

Medulla Oblongata

Function: contains respiratory, vomiting, cardiac, and vasomotor (autonomic) centers.
Anterior protrusions:
- Olivary bodies: Contains olivary nuclei, made of two parts:
  - Inferior olivary nucleus: Part of the olivo-cerebellar system and is mainly involved in cerebellar motor-learning and function.
    - Sends ascending fibers to the cerebellar cortex.
  - Superior olivary nucleus: Considered part of the pons and auditory system.
    - Aids perception of sound.
- Pyramids: Contain motor fibers of the corticospinal and corticobulbar tract.
Posterior features:
- Structures within the rhomboid fossa:
  - Medial eminence and sulcus.
  - Facial colliculus: Formed by fibers from the motor nucleus of the facial nerve as they loop over the abducens nerve.
  - Vestibular area.
  - Hypoglossal trigone.
  - Vagal trigone.
- Mainly contains nuclei of the cranial nerves.
Posterior features:
- Gracile tubercle and fasciculus:
  - One of the dorsal column nuclei that participates in the sensation of fine touch and proprioception of the lower limb.
  - Contains second-order neurons of the dorsal column-medial lemniscus pathway, which receives inputs from sensory neurons of dorsal root ganglia and sends axons which synapse in the thalamus.
- Cuneate tubercle and fasciculus:
  - Part of the dorsal column-medial lemniscus pathway, carrying fine touch and proprioceptive information from the upper limb (above T6, except the ear and face which is carried by the trigeminal nucleus) to the contralateral thalamus via the medial lemniscus.
- Tuberculum cinereum (spinal tract of the trigeminal nerve).

Cranial Nerves

Emerge directly from the brain and brainstem, unlike spinal nerves which emerge from segments of the spinal cord.
Unlike spinal nerves, cranial nerves do not cross over to supply the other side of the body.
Cranial nerves can be classified as:
- General or special:
  - General = the structure associated with a function that is applicable to anywhere in the body.
  - Special = the structure of a pharyngeal arch derivative.
  - Special = the structure associated with a function special to the head and neck.
- Somatic or visceral:
  - Is the structure going to a somatic or visceral structure?
    - All nerves associated with pharyngeal arch structures are considered visceral innervation (even those supplying somatic muscle) - this is because pharyngeal arches are a gut tube derivative.
- Afferent or efferent.

ANS and the Cranial Nerves

Sympathetics originate at the intermediolateral nucleus of the lateral grey column (T1/2 - L3).
- Exit via the ventral horn.
- Enter the sympathetic trunk via the white matter communicans.
  - Exit the sympathetic trunk at the same or another level via grey rami communicans.
- Sympathetic nerves can either synapse within the sympathetic trunk or one of the cervical ganglions.
Parasympathetics originate in the brain or sacroiliac region.
- Originate within the following cranial nerves:
  - Oculomotor (3).
  - Facial nerve (7).
  - Glossopharyngeal nerve (9).
  - Vagus nerve (Does not supply any parasympathetic innervation to head and neck structures) (10).
- Usually synapse at the target organ, except in the target organ where they synapse at one of 4 paired ganglia:
  - Ciliary ganglion (sphincter pupillae, ciliary muscle) via CN3.
  - Pterygopalatine ganglion (lacrimal gland, glands of nasal cavity) via CN7.
  - Submandibular ganglion (submandibular and sublingual glands) via CN7.
  - Otic ganglion (parotid gland) via CN9.

Rule of 4s

Four cranial nerves emerge above the pons:
- Cerebrum:
  - CN1 = telencephalon (embryonic cerebral cortex).
  - CN 2 = diencephalon (embryonic basal ganglia)
- Midbrain:
  - CN3 = midbrain-pontine junction.
    - Palsy = Impaired adduction, supraduction, and infraduction of the ipsilateral eye +/- dilated pupil.
      - ‘Down and out’
  - CN4 = exits posteriorly from the midbrain.
    - Unable to look down when the eye is looking down towards the nose.
Four cranial nerves emerge from the pons:
- Pons:
  - CN5 = pons.
    - Ipsilateral alteration of pain, temperature, light touch on the face, back as far as the anterior ⅔ of the scalp and sparing the jaw angle.
- Pontine-medullary junction:
  - CN6 = pontine-medullary junction.
    - Ipsilateral weakness of eye abduction (lateral rectus).
  - CN7 = pontine-medullary junction.
    - Ipsilateral facial weakness.
  - CN8 = pontine-medullary junction.
    - Ipsilateral deafness.
    - Nausea and vomiting.
Four cranial nerves emerge from the medulla:
- Medulla Oblongata:
  - CN9 = posterior to the olive.
    - Ipsilateral loss of pharyngeal sensation.
  - CN10 = posterior to the olive.
    - Ipsilateral palatal weakness.
  - CN11 = posterior to the olive.
    - Ipsilateral sternocleidomastoid and trapezius weakness.
  - CN12 = anterior to the olive.
    - Ipsilateral weakness of the tongue.

Medial and Lateral Medullary Syndrome

Medial Medullary Syndrome has 4 deficits associated with 4 medial structures:
- Motor pathways (corticospinal) - contralateral weakness of arm and leg.
- Medial lemniscus (DCML) - contralateral loss of vibration and proprioception in arm and leg.
- Medial longitudinal fasciculus - ipsilateral internuclear ophthalmoplegia.
- Motor nuclei - ipsilateral loss of cranial nerve affected (3, 4, 6, or 12).
  - Motor nuclei of 3, 4, 6, and 12 are midline (all divisible into 12).
Lateral Medullary Syndrome has 4 deficits associated with 4 lateral structures:
- Sympathetic - ipsilateral Horner's syndrome, partial ptosis, and miosis.
- Spinothalamic - contralateral alteration of pain and temperature, affecting arm and leg, rarely the trunk.
- Spinocerebellar - ipsilateral ataxia of arm and leg.
- Sensory nucleus for CN5 - ipsilateral alteration of pain and temperature on the face.
  - 5th sensory nucleus = long vertical structure extending in the lateral aspect.
  - May also involve 5/ 7th if pons lesion and 9/ 11th nerves if medulla.

Cerebellum

Part of the hindbrain located posterior to:
- 4th ventricle.
- Pons.
- Medulla.
Separated from the overlying cerebrum by the tentorium cerebelli.
Connected to the midbrain via:
- Superior cerebellar peduncle.
- Middle cerebellar peduncle.
- Inferior cerebellar peduncle.
Functions:
- Plays a significant role in motor control.
  - Does not initiate movement, but contributes to coordination, precision, and accurate timing.
  - Receives input from sensory systems and other parts of the brain and integrates these inputs to fine-tune motor activity.
  - May also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses.
- Cerebellar damage produces disorders in fine movement, equilibrium, posture, and motor learning.
Dentate nucleus is one of four pairs of deep cerebellar nuclei.
- Largest and most lateral - located within the deep white matter of each cerebellar hemisphere.
- Responsible for planning, initiation, and control of voluntary movements.
  - Dorsal region contains output channels involved in motor function, which is the movement of skeletal muscle.
  - Ventral region contains output channels involved in nonmotor function, such as conscious thought and visuospatial function.
Anterior lobe is above the primary fissure.
Posterior lobe is below the primary fissure.
Cerebellum-vermis:
- Located in the medial zone of the cerebellum.
- Functionally, the vermis is associated with bodily posture and locomotion.
- The vermis is included within the spinocerebellum and receives somatosensory input from the head and proximal body parts via the ascending spinal pathways.
Peduncles:
- Superior - primary output from the cerebellum to the midbrain.
- Middle - input from the contralateral cerebral cortex.
- Inferior - ipsilateral proprioceptive information form the spinal cord.
Cerebellar tonsil is a rounded lobule on the undersurface of each cerebellar hemisphere, continuous medially with the uvular of the cerebellar vermis and superiorly by the flocculonodular lobe.
- May herniate through the foramen magnum (tonsillar herniation/ coning).
Flocculonodular lobe (vestibulocerebellum):
- Primary connections are with the vestibular nuclei, but also receives visual and other sensory input.
- Participates mainly in balance and spatial obstruction.
- Damage to this region causes disturbances of balance and gait.

Cerebellar Lesions

Vestibulocerebellum lesions:
- Balance.
- Gait dysfunction.
- Nystagmus.
- Balance and stability.
Spinocerebellum lesions:
- Ataxia.
- Dyssynergia.
- Dysmetria.
- Dysdiadochokinesia.
- Reﬁning ongoing movements.
Cerebrocerebellum lesions:
- Loss of initiation, timing, and sequencing of movements.
- (Musical instruments).
- Loss of cognitive functioning.

Ascending Tracts

Responsible for transmitting sensory information (somatosensory pathways) from the peripheral nerves to the cerebral cortex.
Can be divided into unconscious and conscious tracts:
- Conscious tracts:
  - Dorsal column-medial lemniscal pathway.
  - Anterolateral system.
- Unconscious tracts:
  - Spinocerebellar tracts.

Dorsal Column Medial Lemniscal Pathway

Function: Carries fine touch, vibration, and proprioception.
Course:
- First-order neurons travel via the posterior (dorsal) column in the spinal cord.
  - Signals from the upper limb travel within the cuneate fasciculus (lateral dorsal column).
  - Signals from the lower limb travel within the gracile fasciculus (medial dorsal column).
- These synapse with second-order neurons in the medulla oblongata.
- Second-order neurons decussate within the medulla oblongata.
- Second-order neurons travel within the medial lemniscus to reach the thalamus.
- These synapse with third-order neurons in the thalamus.
- Third-order neurons transmit sensory signals from the ventral posterolateral nucleus through the internal capsule to the primary somatosensory cortex in the brain.

Spinothalamic Tract

Function:
- Anterior spinothalamic tract - carries crude touch and pressure.
- Lateral spinothalamic tract - carries pain and temperature.
Course:
- First-order neurons enter the spinal cord and ascend ipsilaterally 1 or 2 vertebral levels.
- These synapse with second-order neurons in the dorsal horn (substantia gelatinosa) of the spinal cord.
- These second-order neurons decussate immediately and form 2 distinct tracts at this point:
  - Crude touch and pressure enter the anterior spinothalamic tract.
  - Pain and temperature enter the lateral spinothalamic tract.
- These travel superiorly and synapse with the third-order neurons in the thalamus.
- Third-order neurons transmit signals from the ventral posterolateral nucleus through the internal capsule to the primary somatosensory cortex in the brain.

Spinocerebellar Tract

Function: Unconscious proprioception.
Course:
- Posterior spinocerebellar tract = proprioceptive information from the lower limb → ipsilateral cerebellum (entering the cerebellum via the inferior cerebellar peduncle).
- Anterior spinocerebellar tract = proprioceptive information from the lower limb → ipsilateral cerebellum.
  - Double decussation of fibers.
  - Fibers ascend to the midbrain, however, make a sharp turn caudally and enter the cerebellum via the superior cerebellar peduncle.
- Rostral spinocerebellar tract = proprioceptive information from the upper limb → ipsilateral cerebellum.
- Cuneocerebellar tract = proprioceptive information from the upper limb → ipsilateral cerebellum (through cuneate fasciculus).

Descending Tracts

Pathways by which motor signals are sent from the brain to lower motor neurons.
Can be divided into pyramidal and extrapyramidal tracts:
- Pyramidal tracts pass through the medullary pyramids of the medulla oblongata.
  - Originate in the cerebral cortex and carry motor fibers to the spinal cord and brainstem.
  - Responsible for voluntary control of musculature of the body and face.
    - Corticospinal tract = musculature of the body.
    - Corticobulbar tract = musculature of the head and neck.
- Extrapyramidal tracts do not pass through the medullary pyramids.
  - Originate in the brainstem and carry motor fibers to the spinal cord.
  - Responsible for involuntary and autonomic control of all musculature (e.g., posture, gait, and muscle tone).

Anterior Circulation of Brain

Arises from the internal carotid arteries (ICA)
Supplies the anterior and middle parts of the brain

Posterior Circulation of Brain

Arises from the vertebral arteries
Supplies the posterior part of the brain, including the brainstem and cerebellum

Circle of Willis

Critical network of arteries at the base of the brain connecting anterior and posterior circulations
Provides alternative pathways for blood flow, allowing for compensation if one part of the circulation is compromised
Composed of:
- Anterior cerebral arteries (ACA) x2
- Internal carotid arteries (ICA) x2
- Posterior cerebral arteries (PCA) x2
- Anterior communicating artery (ACA) x1
- Posterior communicating arteries (PCA) x2

Internal Carotid Artery

Originates at the bifurcation of the common carotid artery at the level of C4
Enters the cranial cavity through the carotid canal
Supplies structures including:
- Orbital structures (via ophthalmic artery)
- Lateral cerebrum (via middle cerebral artery - MCA)
- Anterior brain structures (via anterior cerebral artery - ACA)
- Posterior brain structures (via posterior communicating artery)

Vertebral Artery

Arises from the subclavian artery, medial to the anterior scalene muscle
Enters the cranial cavity through the foramen magnum
Supplies structures including:
- Spinal cord (via anterior and posterior spinal arteries)
- Cerebellum (via posterior inferior cerebellar artery - PICA)
- Midbrain (via basilar artery)

Basilar Artery

Formed by the convergence of the two vertebral arteries
Supplies the pons and cerebellum
Terminates as the posterior cerebellar artery
Branches include:
- Anterior inferior cerebellar artery (AICA)
- Pontine arteries
- Superior cerebellar artery (SCA)

Abnormalities of the Circle of Willis

Anatomical variations are common, particularly in the posterior circulation
- Common anomaly: hypoplasia of the posterior communicating artery
Aneurysms are abnormal dilations of blood vessels
- Common in the brain, especially at branching points
- Beri aneurysms are common, affecting about 1% of the population
- Can cause subarachnoid hemorrhage, hemorrhagic stroke, or pressure on adjacent structures

Cerebral Vasculature

Anterior cerebral artery
- Supplies the frontal lobe and anteromedial cortex
- Affects logical thought, personality, and sensorimotor functions
Middle cerebral artery
- Supplies portions of the frontal lobe, lateral temporal and parietal lobes
- Affects sensorimotor function (especially face, throat, hands, and arms), speech
- Most commonly occluded in embolic stroke
Posterior cerebral artery
- Supplies the occipital and temporal lobes
- Affects hemianopia of the opposite visual field

Stroke

A group of disorders involving sudden, focal interruption of cerebral blood flow
Results in neurological deficit
Ischemic stroke (80%) is caused by thromboembolism or hypoperfusion
Hemorrhagic stroke (20%) results from vascular rupture
Clinical presentation varies depending on the site and extent of the stroke, and can include:
- Loss of consciousness (LOC)
- Headache
- Paraesthesia
- Weakness
- Paralysis
- Visual/sensory changes
- Aphasia
- Dysarthria
- Dysphagia

Stroke: Laterality of Symptoms

Right-sided stroke
- Left-sided sensory loss/hemiparesis
- Homonymous hemianopia
- Quick, inquisitive behavioral style
- Hemi-spatial neglect
- Amnesia
Left-sided stroke
- Right-sided sensory loss/hemiparesis
- Homonymous hemianopia
- Broca's/Wernicke's aphasia
- Slow, cautious behavioral style
- Amnesia

Stroke: Specific Artery Occlusions

ACA stroke
- Contralateral hemiparesis and hemianesthesia below the knee
- Greater involvement of legs > arms and face → gait apraxia
- Bladder incontinence
- Poor decision making, rational thinking
MCA stroke
- Contralateral hemiparesis and hemianesthesia
- Greater involvement of arms and face > legs
- Aphasia (if dominant hemisphere affected)
- Sensory neglect (if nondominant hemisphere is affected)
- Contralateral homonymous hemianopia
PCA stroke
- Total hemisensory loss
- Homonymous hemianopia
- Amnesia
Lacunar stroke
- Small infarcts of deep white matter, mainly affecting the basal ganglia, thalamus, and internal capsule
- Often caused by systemic hypertension → hemorrhagic strokes of small arteries
- Variable presentation: - Contralateral pure motor loss - Contralateral pure sensory loss - Ataxic hemiparesis - Dysarthria and clumsy hand

Stroke: Investigations

Non-contrast CT Brain
- First test to determine if ischemic or hemorrhagic
CT Brain angiography
- Used for ischemic strokes

Stroke: Management

Acute intravenous thrombolysis
- Alteplase (tPA)
- Must be administered within 4.5 hours of symptom onset
Endovascular thrombectomy
Antiplatelet therapy

Cerebellar Vasculature

Supplied by 3 main arteries:
- Superior cerebellar artery (SCA) - branch of the basilar artery
- Anterior inferior cerebellar artery (AICA) - branch of the basilar artery
- Posterior inferior cerebellar artery (PICA) - branch of the vertebral artery

Brainstem Vasculature

Midbrain
- Supplied by:
  - Superior cerebellar arteries
  - Posterior cerebral arteries
  - Posterior communicating arteries
Pons
- Supplied by:
  - Pontine and paramedian branches of the basilar artery
  - Superior cerebellar arteries
Medulla Oblongata
- Supplied by:
  - Anterior spinal artery and paramedian branches of the vertebral artery - medial part of the medulla oblongata
  - Posterior inferior cerebellar artery (PICA) - posterolateral part of the medulla where the main sensory tracts run and synapse
  - Anterior inferior cerebellar artery (AICA)

Brainstem: Vascular Syndromes

Medial medullary syndrome
- Occlusion of the anterior spinal artery
Lateral medullary syndrome (Wallenberg's Syndrome)
- Occlusion of the vertebral artery or PICA

Haemorrhages and Herniation

Extradural haemorrhage
- Arterial bleed
- Classical lentiform/lemon shape – limited by suture margins
Subdural haemorrhage
- Usually results from tears in bridging veins that cross the subdural space
- Finger to Nose test: dysmetria (overshoot or undershoot)
- Dysdiadochokinesia
- Intention tremor
Subarachnoid haemorrhage
- Thunderclap headache
- Blood in the CSF

Cerebrocerebellum

Anatomical location: lateral hemispheres
Function: planning, modifying and learning movements
Inputs: contralateral cerebral cortex (both motor and sensory)
Symptoms:
- Affected motor memory
- Delays in movement initiation
- Irregularities in timing movement components
- Affected cognitive function
- Spatial cognition
- Affect (the impression of one’s mood perceived by another person)

General Principles of Cerebellum

Pathology
- Tumors:
  - Hemangioblastoma
  - Medulloblastoma
- Vascular:
  - Haemorrhage
  - Infarction
  - Arteriovenous malformation
- Toxic:
  - Chronic alcohol abuse
  - Lead poisoning
- Infection:
  - Abscess
- Development:
  - Arnold Chiari malformation
  - Cerebral palsy
- Inherited:
  - Friedreich's ataxia
  - Ataxia telangiectasia
Presentation
- DANISH:
  - Dysdiadochokinesia
  - Ataxia
  - Nystagmus
  - Intention tremor
  - Slurred speech
  - Heel to toe walking and hypotonia
Ipsilateral cerebellum is affected to the pathological side
If bilateral, think drugs and toxins