Formative

Question 1

<p>In what anatomical plane is the image presented in?</p>

Answer 1

<p>Sagital</p>

Question 2

i) Name the thin grey/white line labeled A ii) What is its Anatomical Importance? iii) What specific tissue of the nervous system does it comprise?

Answer 2

i) Tentorium cerebelli (2 mark)
ii) It is used to divide the intracranial cavity into supra- &infra-tentorial compartments. Its main function is to support occipital lobes of the cerebral cortex ( either of these =2 marks)
ii) (In-folding of the) Meningeal layer (1) of the Dura Mater (1 mark)

Question 3

i) Name the black spot labelled B
ii) What would you expect to find in it?
iii) Name the chamber labelled C

Answer 3

i) Confluence of the sinuses/ Superior Saggital Sinus /Transverse sinus meet here(1 mark) (NB: Occipital sinus also connects here)
ii) Venous Blood (1 mark)
iii) Lateral ventricle (1 mark)

Question 4

The features labelled D can give a patchy whitish presentation in some individuals.

i) Name these features. (2 marks)
ii) What bone is labelled E? (1 mark)
iii) Which fossa of the cranium is it part of? (1 mark)

Answer 4

i) Arachnoid villi or when thickened (hence whitish colour) as in this case, arachnoid granulations (2 mark)
ii) Ethmoid (1 mark)
iii) Anterior Cranial Fossa (1 mark)

Question 5

The anatomical feature labelled F is a tumour in the brain?

i) In what neurological structure is the feature labeled F located? (1 mark)
ii) What neuronal tracts supply this structure for its sensory functions (1 mark each totalling 2 marks)
iii) Assuming this lesion produced clinical signs in this patient, what distinctive triad of neurological signs indicative of damage to this neurological structure would have been elicited on examination? (any 3, 1 mark each)

Answer 5

i) Cerebellum (1 mark)
ii) Dorsal Spinocerebellar tract (1 mark) & Ventral Spinocerebellar tract (1 mark)
iii)
Dysmetria, Dysarthria & Ataxia (any 3, 1 mark each) NB: Whilst D-A-N-I-S-H is a useful mnemonic for signs seen following damage to the cerebellum, only the combination of “triad of signs” given above is specific to the cerebellar damage alone.

Question 6

What anatomical landmark of the body defines T10 Dermatome?

Answer 6

i) Abdominal navel or Belly Button (2 marks)

Question 7

Given that the youth had a Brown-Sequard disturbance, what does that tell you about the extent of compression of the spinal cord in this case? (4 marks)

Answer 7

By definition, Brown-Sequard disturbance suggests a hemicord ( 2 marks) disturbance. The hemi-cord being referred to here is that in the transverse plane (2 marks).
The compression mentioned in the above case scenario will have affected half of the cord in the transverse plane.

Question 8

i) Why were the left and right lower limb reflexes both depressed (3 marks)

Answer 8

Max. Mark
i) Tone in both limbs is said to have been reduced. Therefore, the reflexes are also likely to be reduced as tone requires that the muscle spindle afferents, alpha and gamma motoneurones are all intact and the monosynaptic stretch reflex arc works well and the synaptic transmission is not under heavier inhibition. The fact that the limb reflexes are reduced indicates that at the acute stage, in any event, the involvement of upper motoneurones is not reduced. If anything, it would be increased. There is a possibility of limited spinal shock to explain this reduction in limb reflexes. There is also the possibility here that CSF flow to the cord was also compromised, leading to disruption of neuronal function, hence depression of limb reflexes ( See below for fuller explanation) (A question such as this gives you lots of opportunities to show your knowledge. Some facts may be in conflict and so it is important to show good command of the subject and whatever you do, take a sensible and sustainable position on such multifactorial, complex pathways) (3 marks)

Question 9

ii) Why was the right side more affected than the left? (2mark)

Answer 9

ii) The right side was more affected than the left because it is the side with the Brown-Sequard disturbance. (2 mark)

Question 10

i) What is your understanding of motor tone?

Answer 10

i) Motor tone is also known as muscle tone. When applied to limbs, It is defined as the resistance to passive limb movements (1 mark). Almost all skeletal muscles have a background resting level of activity from the CNS and this neuronal activity originates from gamma motoneurones whose activity is controlled by the central nervous system. In turn, this activity in gamma motoneurones brings about background muscle spindle activity, which in turn recruits alpha motoneurones into activity via the stretch reflex. Put simply, this whole pathway, therefore, prevents change in muscle length of the limb in question. Body posture is only possible through this notion of motor tone. Without it, we could not maintain posture. Instead we would collapse into a heap of muscle and bone tissues

Question 11

ii) Name 4 neuronal elements that are important in the establishment of normal motor tone?

Answer 11

ii) Descending motor tracts (1 mark); gamma motoneurones (1 mark), muscle spindle afferents (1 mark) and alpha motoneurones (1 mark)

Question 12

i) What diagnosis would you make of this man’s medical problem? (2 marks)
ii) If he was given appropriate treatment in reasonable time, what would be his long term prognosis? (1 mark) Explain your answer (1 mark)

Answer 12

He is likely to have suffered a blow to the vertebral column that did not result in stabbing of the spinal cord, this in turn resulted in a subdural haematoma in the spinal cord, that in turn led to compression of the spinal cord. Neurological symptoms given above must have been to compression injury to the cord. (2 marks)

Early diagnosis is critical in injuries of the CNS as compressions can cause serious irreversible damage. The fact that the disturbance here was to one side (Brown-Sequard disturbance) and providing the haematoma is evacuated in good time, the prognosis is excellent providing physiotherapy (1 mark)

In contrast, disturbances of the complete cord do not have positive outcomes compared to hemi-cord disturbances (1 mark

Question 13

A 65-y.o. HIV-positive man began having spontaneous involuntary movements of his right arm and leg approximately 1 month prior to presentation in clinic. On examination he had continuous, uncontrollable flapping and circular movements of his arm and occasional jerking movements of his right leg, unsteady gait with a lean to the right.

What is the name given to the movements the patient makes? (1 mark)
ii) In which common neurodegenerative disorder are these types of behaviour often found? (1 mark)
Which two areas of the brain often show damage in this disorder? (1 mark each)

Answer 13

Hemiballismus (1 mark)
Huntington’s disease(1 mark)
The subthalamic nuclei and striatum (1 mark each)

Question 14

Which side of the brain is lesioned in this patient? (movements and leaning on/to the right)

Answer 14

Left

Question 15

At what level of the spinal cord did you perform the lumbar puncture to obtain the CSF? (1 mark)

Why is it performed at this level and why is it at a different level in young children? (2 marks)

Answer 15

L3-L4 (1 mark)

The end of the spinal cord proper is L1-L2, thus to avoid the cord the punch is performed below this as the need can pass through the cauda equine causing little or no damage, in young children the cord is less misaligned thus requiring a lower punch(2 marks)

Question 16

The regions involved in this disorder form part of which group of brain areas? (1 mark) What function are these areas involved in (2 marks) and which other area of the brain do they work with?(2 marks)

Answer 16

They form part of the basal ganglia (1 mark)

Together with the cerebellum (2mark) they are involved in motor control (2 mark)

Question 17

What is the most well-known of the hypokinetic disorders? (2 marks)

Which area of the brain is affected in this disorder (2 marks) and how? (2 marks)

Answer 17

Parkinson’s (2 marks?!!!)

The substantia nigra is affected in this disorder (2 marks). There is a loss of dopaminergic neurons in this region (2 marks) which leads to a slowing down of motor outflow, hence hypokinesia

Question 18

Figure 1 below shows a pre-labelled picture of a major system of the central nervous system in the adult brain

i) Name this system (2 marks)
ii) Name the 2 major contents of this system (2 marks)
iii) By what name are cells lining this system of the brain called? (2 marks)

Answer 18

i) Ventricular System
ii) Cerebrospinal fluid & Choroid Plexus
iii) Epindymal Cells

Question 19

i) What is a hydrocephalus? (1 mark)

Answer 19

i) Hydrocephalus means a state of increased CSF pressure within the ventricular system, often due to a mismatch between CSF production and its re-absorption into general circulation

Question 20

ii) What then is a communicating hydrocephalus? (1 mark) What is it also known as? (1 mark)

Answer 20

ii) In a communicating hydrocephalus the ventricular system remains patent and CSF flow is not impeded, but rather absorption at the level of the arachnoid granulations is impeded. It is also known as external hydrocephalus since the problem occurs externally to the ventricular system.

Question 21

iii) What is a non-communicating hydrocephalus? (1 mark) What is it also known as? (1 mark)

Answer 21

iii) A non-communicating hydrocephalus occurs when there is blockage of CSF flow within the ventricular system itself. The most likely site for such blockage is the cerebral aqueduct of Sylvius that joins the 3rd ventricle to the 4th ventricle. This aqueduct is physically the narrowest part of the ventricular system. It is also known as an internal hydrocephalus

Question 22

This case of hydrocephalus resulted from scarring of the meninges subsequent to parasitic infection.
i) What would be the most likely explanation for the general mechanisms giving rise to this case of hydrocephalus? (4 marks)

Answer 22

The patient acquired an external (1 mark) hydrocephalus that resulted in raised intracranial pressure. The problem must primarily affect the area of the arahcnoid granulations (1 mark).

The most likely causes are: ( 2 marks for an valid answer) Parasytic cyst Tuberculous meningitis infections Subarachnoid haemorrhage, or head injury Tumour of the brain

Question 23

Left untreated, and assuming the condition does not worsen, i) Name 2 distinctive features you might expect to see in this patient’s CT head scans (1 mark each totaling 2 marks) ii) Which intracranial structures are likely to be damaged? (1 mark) iii) Explain your answers (1 mark)

Answer 23

i) Dilated ventricles ( 1 mark) and atrophy of brain tissue (1 mark)
ii) Atrophy of the cerebral cortex as it is exquisitely sensitive to compression. (1 mark)
iii) Explanations: (1 mark) Dilated ventricles result from increased csf volume and therefore, they appear large to reflect this increased capacity. This increased CSF capacity compresses cortical tissue that in turn degenerates as a result this disruption. If the primary problem is not resolved the CSF volume will steadily increase and the cerebral cortical tissue in turn atrophies.

Question 24

i) Regarding Non-Communicating hydrocephalus, what pathology of the brain is likely to lead to this condition? (0.5 marks)
ii) Which neuro-anatomical structures are likely to be implicated in this condition? (0.5 marks) Explain both your answers

Answer 24

Tumour in the Cerebral aqueduct. Tumours of the 3rd ventricle are a common explanation here (0.5 marks)

Pituitary tumours are usual suspects here. Others will include the pineal gland, optic nerve and the hypothalamus (0.5 marks)

Question 25

The patient exhibited a left ptosis and smaller reactive left pupil (of the eye) and decreased left facial sweating.

What syndrome is the patient displaying? (2 mark)

Answer 25

Horner’s syndrome

Question 26

i) Where are the two most likely sites of lesion that would cause these autonomic symptoms? (4 marks)
ii) You are told that impaired sweating is more common with a preganglionic lesion, where then would you localize the lesion in this case scenario. (2 mark)

Answer 26

i) Either the carotid plexus or the sympathetic chain
ii) In the sympathetic chain (the information you have been given here is meant to help you to distinguish between vascular localization of the lesion from that in the sympathetic chain)

Question 27

The pellet took a slightly downward trajectory and lodged between the left T1 and T2 nerve root exits points. Draw the dermatomal distribution that would be expected if these roots had been damaged. (2 marks for front, 2 marks for back)

Answer 27

Draw

Question 28

The pellet damaged part of the T1 ventral horn.

Identify the types of motoneurones likely to be damaged by a lesion in this area? (4 marks)

Answer 28

The α and γ motoneurones

Question 29

If an infection were to establish as a result of this wound and this became supperative, where, most inferiorly might you expect puss to collect? (2 marks) Justify your answer (2 marks)

Answer 29

Posterior mediastinum (2 marks)

The infection would have established within the pre-vertebral fascia of the neck that extends as far inferiorly as the posterior mediastinum. (2 marks)

Question 30

Name the functions of the thalamus

Answer 30

Main relay site for projections of all sensory signals to the thalamus apart from the olfactory system

Plays a key role in the integration of visceral and somatic functions

Involved in the performance of voluntary movements
Together with the reticular formation, it controls the level of overall excitability of the cerebral cortex

Question 31

i) What clinical signs will you expect from a patient with an advanced case of ALS? Explain your answer.

Answer 31

The condition lesions both upper & lower motoneurones. When upper & lower motoneurone signs are superimposed on each other, the lower motoneurone signs predominate. Upper motoneurone signs can only be detected if the lower motoneurone innervation of the muscle is intact

Question 32

i) What other additional target organs should you be concerned about in a patient with ALS?
ii) What is the prognosis for this patient? iii) Explain your reasoning in ii) above.

Answer 32

i) Respiratory muscle innervation by the thoracic ventral horn columns is critical to life
The bladder
The anal sphincters

ii) Currently, there is no known treatment
Patients eventually die from complications of respiratory tract infections or cessation of breathing through death of thoracic motoneurones

Question 33

Regarding function of the urinary bladder in motoneurone disease, what type of neurological bladder should be expected here? Justify your answer.

Answer 33

It is curious that ONUF’s nucleus is spared in MND. Although it is a somatic lower motoneurone pool, it does not succumb t o MND and for that reason it is considered an anomally. The Detrusor Muscle also continues to receive normal innervation from the lateral horn of the sacral cord (PARASYMPATHETIC). Taken together, this information suggests that bladder function in MND rema ins normal. Urinary incontinence seen in MND (as the sub - type given above) is not due to disrupted bladder function, but due to immobility. This leads to failure to access sanitary facilities on time, hence incontinence, not bladder function per se.

Question 34

Outline the cardinal lower motoneurone signs. Give a brief explanation for each of these.

Answer 34

Flaccid Paralysis

Muscle Weakness

Hypotonia

Areflexia or hyporeflexia

Muscle wasting (denervation atrophy)

Fasciculations

Question 35

Map the general path taken by cerebrospinal fluid as it circulates from lateral ventricles to the venous circulation via the fourth ventricle

Answer 35

Right and lef Lateral Vent ricles (1 and 2) communicate with each other and the third venticle vi via the foramen of Monro, in turn the third ventricle communicates with the 4 th ventricle by way of the cerebral aqueduct of Sylvius. From the 4 th ventricle CSF passes into subarachnoid space via its 3 openings, the 2 lateral apertures of Luschka that drain into the cistern of the great cerebral vein and the midline aperture of Magendie that drains into the cisterna magna

Question 36

Which parts of the brain are exempt from attendance of the blood brain barrier? Why is this necessary?

Answer 36

Pituitary Gland

(stimulatory hormone release upon sensing, e.g. low oestrogen; FSH)

Hypothalamus

chemoreceptor trigger zone in the fever region of the hypothalamus
They need to be able to sense stimuli / levels and contents of blood to react and to maintain homeostasis

Question 37

How might immune previllege of the brain be exploited in the treatment of some degenerative conditions of the brain?

Answer 37

Allografts of brain tissue is possible as there no likelihood of tissue rejectio

Question 38

Contrast the communicating and non-communicating hydrocephalus

Answer 38

Communicating

Blockage at the level of the arachnoid granulations following infections of the meninges

Non - Communication

Within the lumen of the ventricular system, usually a tumour - most probable along the course of the cerebral aquenduct of Sylvius

Question 39

Regarding Motor Tone What role do gamma motoneurones play in muscular tone?

Answer 39

They are responsible for the genesis of motor tone due to their small size, hence high input resistance and therefore small depolarisation of their membranes will lead to threshold for action poten tial firing. This will result in the activation of intrafusal muscle fibres, hence activation of the muscle spindle afferents and in turn recruitment of alpha motoneurones through the stretch reflex. Alpha motoneurones are not thought to bring about tone i n themselves

Question 40

Name 2 upper motoneurone structures which when selectively lesioned produce hypotonia. Why is it important to be aware of these?

Answer 40

Selective Lesion of the corticospinal Tract (Rare)

Cerebellum (ipsilateral signs)

The se are rare exceptions to the rule

Question 41

What is spastic paralysis? Which functional group of muscles tend to be predominantly active in this form of paralysis?

Answer 41

It is the paralysis of muscle through simultaneous co - contr action of flexors and extensors acting across the same joint. This simultaneous activity deprived the joint of movement, hence paralysis

Limb anti - gravity muscles are the predominantly active muscles that are active during spastic paralysis

Question 42

What type of muscle atrophy is seen in patients with long term spastic paralysis

Answer 42

Disuse muscle atrophy

Question 43

What is a reflex? How does it differ from a reflex arc?

Answer 43

It is a motor act (an unlear ned automatic response to a specific stimulus which does not require the brain to be intact) The arc is simply a neuronal circuit that brings about a reflex act