Neurology: Clinical Neuroanatomy, Neurolocalisation

Question 1

What are the main CNS divisions of the brain?

How is the spine divided into 4 segments?

Answer 1

Forebrain- cerebral cortex, diencephalon

Brainstem- midbrain, Pons, Medulla oblongata

Cerebellum

C1-C5, C6-T2, T3-L3, L4-S3
Neck, forelimb, trunk, hindlimb- ish

Question 2

How does the spine matter appear what do the different matters do?

Answer 2

Peripheral white matter-
nerve tracts- motor going down, sensory going up

Central gray matter- butterfly
interneurons and motor neurons that innervate muscles

Question 3

What makes up the PNS?

Answer 3

Nerves, NM junctions, Muscles

• Axons of spinal (36) and cranial nerves (12) and their receptors and effector organs
• Nerves may be motor, sensory or both
• Motor neuron cell body is in ventral horn of SC
• Myelination through schwaan cells, no BBB

Question 4

What is the function of the ANS?

What are the different parts?

Answer 4

Involuntary, controls visceral functions

Sympathetic- thoracolumbar- fight or flight

Parasympathetic- craniosacral- rest and digest

Antagonistic

Question 5

How is the ANS involved in filling and emptying of the bladder?

Answer 5

Filling-
detrusor muscle relaxed and sphincter tone increases
as bladder gets bigger, messages go to pons until a critical size is reached and bladder is ready and empty

Emptying-
detrusor muscle contracts under parasympathetic control in sacral SC
Sphincters relax due to reduced activity in motor neurons and sympathetic neurones

Question 6

Describe the ANS- sympathetic supply to the eye

What does it innervate?

How does dysfunction present?

Answer 6

1. 1st order neuron- starts at the brain stem and courses caudally in cervical spinal cord
2. 2nd order neuron- leaves the spinal cord at T1-T3 through brachial plexus, courses rostrally through neck in vagosympathetic trunk
3. Synapses at cranial cervical ganglion ventromedial to tympanic bulla
4. 3rd neuron towards eye

Innervates- smooth dilator of pupil, orbitalis muscle, smooth ciliaris muscle, smooth muscle BVs and sweat glands of head

Dysfunction- Horner’s syndrome

Question 7

1. What does grey and white matter contain?
2. What are the layer of the meninges?
3. How are cranial nerves named?
4. Describe the CSF pathway

Answer 7

1. Grey- contains cell bodies, surface of brain or centre of spinal cord, process information
   White- myelinated axon tracts, deep part of brain, superficial SC, connects everything
2. Dura mater- thick outer,
   Arachnoid- thin
   Subarachnoid space- CSF, blood vessels, nerve roots
   Pia mater- thin, inner layer
3. Named I to XII from most rostral to most caudal
4. Lateral ventricle to intraventricular foramen to 3rd ventricle to mesencephalic aqueduct to 4th ventricle to lateral apertures to subarachnoid space

CSF covers all surface of brain and SC- flows in pulsatoins of blood in choroid plexus, caudally

Question 8

List the cranial nerves

Answer 8

• Olfactory
• Optic
• Occulomotor
• Trochlear
• Trigeminal
• Abducens
• Facial
• Vestibulochlear
• Glossopharyngeal
• Vagus
• Accessory
• Hypoglossal

Question 9

What is the CN I involved in?

Where are its cell bodies found?

What do axons pass through?

Answer 9

Olfactory- conscious perception of smell

Cell bodies in olfactory epithelium rather then on a ganglion

Axons pass through cribform plate and synapse in olfactory bulb

Rarely see dysfunction- responsible for too much in the brain

Question 10

What is CN II involved in?

Where do its axons travel?

Why is dysfunction ‘easy’ to diagnose?

What myelinates it?

Answer 10

Optic- vision

• 1st neuron in bipolar cells of retina recivieing information from rods and cones
• Axons couse caudally and enter skull through optic canal then join at optic chiasm

Easy to diagnose dysfunction- either eye, then nerve, then brain process

Myelinates by olidodendrocytes, surrounded by BBB- ‘extension or the brain’

Question 11

What muscles does CN III innervate?

What does the parasympathetic component innervate?

Where is the nucleus, how do axons travel?

How can dysfunction be diagnosed?

Answer 11

Occulomotor- ipsilateral dorsal, ventral and medial rectus, ventral oblique extraocular muscles
Levator palpebrae superioris- elevation of eyelid

Parasympathetic controls pupillary contraction

Nucleus in midbrain, axons through orbital fissue

Pupillary contraction or lateral strabismus

Question 12

What does cranial nerve IV innervate?

Where is the nucleus and axon route?

Answer 12

Trochlear- contralateral dorsal oblique

Nucleus in caudal midbrain, axons exit through orbital fissure

Question 13

What is the function of CN V?

What are the three branches?

Where are its nuceli?

Answer 13

Sensory innervation of the face
Motor innervation of the masticatory muscles

Opthalmic- sensory
Maxillary- sensory
Mandibular- sensory and motor

Motor nuceli in Pons, Sensory nuclei extend through brain stem

Question 14

What does CN VI innervate?

Where is its nucelus and the axon routes?

Answer 14

Abducens- ipsilateral rectus and retractor bulbi muscle

Nucleus in rostral medulla, axons exit skull through orbital fissure

Question 15

What does CN VII innervate?

Answer 15

Facial nerve

Motor innervation to muscles of facial expression

Sensory innervation to rostral 2/3 of tongue and palate

Parasympathetic innervation to lacrimal, mandibular and sublingual glands

Question 16

What is the function of CN VIII?

Where are its nuclei?

Answer 16

Vestibulochlear- Hearing and vestibular function

Receptors in inner ear pass internal acoustic meatus to get to medulla

Vestibular nuclei in medulla
Cochlear nucleus in medullar

Question 17

What is the function of CN IX?

What nerve does it share is nuclei with?

Answer 17

Motor innervation of pharynx and palate
Sensory innervation of caudal 1/3 of tongue and pharynx

Parasympathetic innervation of parotid and zygomatic glands

Shares nuceli with CN X in caudal medulla

Question 18

What is the function of CN X?

Where is its nucleus?

Answer 18

Vagus- Motor innervation of larynx, pharynx and oesophagus
Sensory innervation of larynx, pharynx, thoracic and abdominal viscera

Parasympathetic innervation to all thoracic and abdominal viscera

Question 19

What is the function of CN XI, where is its nucleus?

What is the function of CN XII, where is its nucleus?

Answer 19

Accessory- trapezius and part of sternocephalicus and brachiocephalicus
Nucleus in caudal medulla

Hypoglossal- motor innervation of the tongue
Nucleus in caudal medulla, axons exit through hypoglossal foramen

Question 20

How can autonomic nervous system diseases cause incontinence?

What drugs can be used to treat this?

Answer 20

Upper motor neurone- sphincters tighten
Lesions cranial to sacral spinal cord, bladder difficult to express, loss of inhibitory pathway to sympathetic and somatic efferent

Lower motor neurone bladder- lesions in sacral spinal cord and/or sacral spinal nerves
Distended bladder overflows and dribbles, only internal sphincter works

Increase detrusor contraction- bethanecol, cisapride
Decrease detrusor hyperreflexia- propantheline bromide, oxybutin chloride
Increase urethral tone- phenylbenzamnine, Diazepam

Question 21

Describe the route of sympathetic innervation to the eye?

Answer 21

• 1st order neuron starts in brain stem, courses causally in cervical spinal cord
• 2nd order neuron- leaves spinal cord at T1-T3 through brachial plexus, courses rostrally through neck in vagosympathetic trunk, synapse at cranial cervical ganglion venteromedial to the tympanic bulla
• 3rd order neuron- courses rostrally to the eye

Innervates- smooth dilator of pupil, orbitalis muscle, smooth ciliaris muscle, smooth muscle of blood vessels and sweat gland

Question 22

What controls the lower motor neurone system?

Answer 22

• Efferent neurons of the PNS
• Connect CNS with muscle to be innervated
  CNS function is manifested through the LMN
• Neuronal cell bodies in ventral GM of spinal cord
• Axon leaves spinal cord through ventral root and travels as PN into muscle

Question 23

Describe the process of a reflex?

Answer 23

• Stimulus- dendritic zone is sensory nerve or muscle
• Sensory peripheral nerve, dorsal root, enters spinal cord, synapses with other neuron in grey matter
• Directly or through interneuron
• Exits spinal cord- ventral root, motor peripheral nerve, neuromuscular junction, muscle contraction

Question 24

What forelimb peripheral nerves are responsbile for a forelimb flexor response?

What spinal cord segments do the nerves originate from?

Answer 24

All forelimb peripheral nerves- musculocut, radial

C6-T2

Question 25

What is the difference between pain and a reflex?

Answer 25

Local reflex- localised to spinal segment Conscious perception of pain- projection to forebrain, important prognastic factor

Question 26

Describe the process of nociception

Answer 26

* Dendritic zone mainly in surface of body- receptor stimulated by mechanical, thermal, chemical * Axons in PN- dorsal roots- enter spinal cord and course cranially and caudally for short distance * Some axons synapse on interneurons in GM activating local reflex, other course medially * Axons coursing medially in SC to brainstem to thalamus to sensory cerebral cortex * Diffusely distributes through SC- big lesion neccessary to completely interrupt

Question 27

What is the upper motor neurone system? What are its functions? How is movements seperated?

Answer 27

Confined to the CNS, axons organised in tracts in white matter that synapse with LMNs in SC grey matter Functions- initiation of voluntary movement, maintenance of muscle tone for support against gravity Pyramidal- skilled movement- poorly developed in animals, start in cerebral cortex through pyramids in brainstem Extrapyramidal- most start in brainstem, dont pass throug pyramids

Question 28

How is general proprioception transmitted? What is unconscious and conscious proprioception?

Answer 28

Detects position and movement of muscles and joints GP afferent neuron- dendritic zone in muscle, tendon or joint- axons in PN- cell body in dorsal root ganglion Unconscious proprioception- spinocerebellar tracts to ipsilateral cerebellum Conscious proprioception- spinal tracts- cross to contralateral side in medulla to thalamus to contralateral sensory cerebral cortex

Question 29

What does LMN or UMN dysfunction lead to? What causes ataxia?

Answer 29

Paresis or paralysis Dysfunction of either general proprioception, cerebellum or vestibular system

Question 30

Describe the miracle of vision from the retina to optic chiasm

Answer 30

1. Retina- 10 layers with 3 types of neurons 2. Optic disc- begining of optic nerve 3. Optic nerve- enters skull through optic canal and joins other side at optic chiasm 4. Optic chiasm and tract- majority of axons crosses to other side in optic tract

Question 31

What is the conscious and reflex pathway of vision? How can you test for these pathways?

Answer 31

Conscious- conscious perception of vision Eye, CN II, crosses at optic chiasm lateral geniculate nerve, optic radiation, contralateral cerebral cortex Reflex pathway- pupil constriction Eye, CNII, crosses at optic chism brainstem, parasympathetic occulomotor, bilateral response Menace response- conscious Pupillary light reflex- reflex Lack of both must be CNII

Question 32

What makes up the forebrain? What is it responsible for?

Answer 32

Cerebral cortex and diencephalon Behaviour, decision making, conscious perception for all sensory systems, some motor functions Thalamus- relay station Hypothalamus- autonomic centre

Question 33

What is ARAS?

Answer 33

Ascending reticular activating system Recieves all information from sensory systems Information courses through the brainstem to thalamus and then projects to cerebral cortex Functoins- arouse cortex, awake and prepare brain Role in alzheimers and ADHD

Question 34

What is the vesticular system? What are the 2 disisions?

Answer 34

Sensory system- maintains balence, normal orientation, positon of eyes, neck, trunk and limbs relative to head Peripheral and Central

Question 35

How does the peripheral vestibular system function?

Answer 35

Inner ear- 3 ducts orientated at right angles to each other- rotation makes endolymph flow within 1 or more ducts Semicircular ducts leads to crista ampularis and macula Drunk alters viscosity Vestibulochlear nerve- Dendritic zone in connection with hair cells of crista ampularis and maculae Movement of fluid in semicircular ducts causes deflection of cupula bending hairs- nerve impulse

Question 36

How does the central vestibular system function?

Answer 36

Vestibular nuclei- 4 either side of brainstem recieve information from CN VIII and project to: * Spinal cord- facilitatory to ipsilateral extensor, inhibitory to ipsilateral flexors, inhibitory to contralateral extensor * Cerebellum- inhibitory * Medial longitudinal fasiculus- nuceli of CN III, IV, VI * Forebrain- perception of balance * Reticular formation- vomiting centre

Question 37

What are the functions of the cerebellum?

Answer 37

Control of motor activity- regulator Recieves GP information from spinocerebellar tracts Coordinated and smoothes out movements induced by UMN Maintentance of balance- through connections with vestibular nuclei Rare projections to LMNs in spinal cord- control of motor activity through influence on UMNs

Question 38

How is neurolocalisation initially divided?

Answer 38

Brain- forebrain, brainstem, cerebellar vestibular Each shows different neurological signs depending on function Spinal cord- further divided C1-C5, C6-T2, T3-L3, L4-S3 Dysfunction and reflexes allow localisation Neuromuscular- Peripheral nerve, NMJ, Muscle

Question 39

What are the overal functions of the forebrain?

Answer 39

Thinking Behaviour Vision Hearing Consciour perception of touch, pain, temperature, body position Fine motor activity

Question 40

What are the potential complications of forebrain dysfunction?

Answer 40

* Disorientation, depression * Contralateral blindness * Normal gait * Circuling, head turn, head pressing, pacing * Decrease in postural response in contralateral limbs * Seizures (always forebrain), behaviour change

Question 41

What are the functions of the brainstem? What are the complications of dysfunction?

Answer 41

Functions- Basic functions for life, ARAS, regulation centres for resp and CV, CN III-XII, all sensory and motor tracts pass through, vestibular nuclei Dysfunction * Depression, stupor coma, * CN defecits (III- XII) * Vestibular signs * Paresis or ipsilateral limbs * Decerebrare rigidity- weakness * Decreased postural responses * Resp and CV abnormalities

Question 42

What is the function of the cerebellum and what is seen with dysfunction?

Answer 42

Control motor activity, Regulator- not initiator Coordinated and smoothes out movement induced by UMN system- spinal cord function and postural tonus, skilled movement Inhibits vestibular system Dysfunction- Normal mentation Ipsilateral abnormal menace with normal vision and PLR Vestibular signs Ataxia, broad stance, **hypermetria** [overshooting] decerebellate rigidity delayed initiation and then often hypermetric postural responses

Question 43

What is the function of the vestibular system? What signs do both regions show with dysfunction?

Answer 43

Maintain balance Position of eyes, neck, trunk and limbs relative to position and head movement Both regions dysfunction show: * Head tilt- ipsilateral usually, contralateral in cerebellar, head sway * Nystagmus- horizontal, rotatory or vertical * Ataxia with leaning and falling * Positional strabismus

Question 44

How can peripheral and central vestibular lesions be distinguished?

Answer 44

Paresis possible with central, not in peripheral **Proprioceptive defecits possible with central**, not with peripheral Mentation with central may be affected, alert with peripheral CN defecits- V-XII with central, VII with peripheral Nystagmus: **Central- vertical**, horizontal or rotatory Peripheral- horizontal or rotatory

Question 45

What is and causes a paradoxical head tilt?

Answer 45

Head tilt contralateral to lesion Lesion on flocculonodular lobe or caudal cerebellar peduncle Cerebellim inhibits ipsilateral vestibular nuclei causing desinhibition Leads to inhibition of ipsilateral extensors and facilitation of contralateral extensors- tilts head

Question 46

What is the difference between upper motor neurons and lower motor neurones? Where do lower motor neurones originate from the SC?

Answer 46

UMN- efferent neuron that originates in the brain and synapses with a LMN modulating its activity LMN- efferent also but from CNS to effector organ (muscle or gland), cell body is in the SC grey matter or nucleus of cranial nerve and axons become PN LMNs for forelimbs- C6-T2, Hindlimbs L4-S3

Question 47

How are reflexes used to location lesions using limbs? If all 4 limbs affected If only hindlimbs are affected Affected = ataxia, paresis, paralysis

Answer 47

If all 4 limbs are affected- C1-T2 * But thoracic reflexes normal, lesion must be C1-C5- above brachial plexus * But reflexes in thoracic limbs reduced lesion must be C6-T2 If hindlimbs affected- T3-S3 * Reflexes in HL normal must be T3-L3 * If reflexes in pelvic limbs reduced must be L4-S3

Question 48

What are the possible symptoms of lesions in the following regions?: C1-C5 C6-T2 T3-L3 L4-S3 The attached picture may help- try without?

Answer 48

C1-C5- Tetra or hemiparesis/plegia, **normal spinal reflexes in all limbs** Horners syndrome, respiratory difficulties, urinary retention C6-T2- Tetra or hemiparesis/plegia- possible mono **Reduced spinal reflexes in thoracic limbs- muscle tone atrophy** Possibly reduced/absent cutaneous trunci reflex Nerve root signature, Horners, resp difficulties, urinary retention T3-L3- Paraparesis/plegia, normal muscle tone/no atrophy **Normal spinal reflexes in all limbs** Possibly reduced/absent cut trunci lesion, urinary retention L4- S3- paraparesis/plegia- possible mono **Reduced spinal reflex in HL, reduced anal tone/perineal reflex in more caudal lesions** Nerve root signature, reduced tail tone, urinary retention, incontience in caudal lesions

Question 49

What needs to be considered when interpreting reflexes?

Answer 49

1. Pain can cause withdrawal of reflex to be reduced 2. If lesion is subtle- just spinal pain- may not be severe enough to affect reflex pathway 3. Patella reflex can be reduced in old age 4. Spinal shock in acute cases

Question 50

What is spinal shock?

Answer 50

Flaccid paralysis with loss of spinal reflexes caudal to lesion in acute spinal cord lesions Temporary- hours Anal sphincter reflex 15 min Patella reflex between 30 min and 2h Flexor withdrawal upto 12 hours Loss of descending facilitatory inpus causing hyperpolarization of spinal motor neurons and reduction in their exitability

Question 51

How are spinal cord lesions graded?

Answer 51

Grade 1- no defecits, just spinal pain Grade 2- ambulatory paresis Grade 3- non-ambulatory paresis Grade 4- paralysis- 80% of walking without surgery Grade 5- paralysis and loss of pain sensation- without surgery 5% chance of walking

Question 52

What are neuropathies, junctionopathies, and myopathies of the neuromuscular system?

Answer 52

Neuropathies- peripheral nerve Junctionopathies- NMJ Myopathies- muscle DISEASE

Question 53

What can nerves can neuromuscular neuropathies affect? How can it present differently? How can it effect region size differ?

Answer 53

12 pairs of CNs and 36 pairs of spinal nerves flaccid paralysis and reduced tone and muscle atrophy- Motor May have proprioceptive deficits, decreases sensation and paraesthenia (self-mutilation)- Sensory Reduced spinal or cranial nerve reflexes Can affect 1 nerve- trigeminal tumour, facial paralysis Can affect a group of nerves- brachial plexus tumour Most/all nerves- polyneuropathy

Question 54

What are the components of a NMJ? What are the three junctionopathies?

Answer 54

NMJ- axon terminal, synaptic cleft, endplate of skeletal muscle Pre-synaptic- botulism Post-synaptic- myasthenia gravis Enzymatic- organophosphates MG- blockage of ACH receptors, walks ok then collapses

Question 55

What are the symptoms of myopathies? What is generalised and focal myopathies?

Answer 55

Generalised weakness and/or excercise intollerance- stiff gait No propriceptive defects, normal spinal reflects Generalised- inherited/degen, inflam/infectious, metabolic Focal- one muscle- masticatory myositis