Seen PBL1

Question 1

what does Diplopia mean? how can it present? [4]

Answer 1

Diplopia: Means double vision. This can either be horizontal (side-by side) diplopia or vertical (up-and-down) diplopia. It can also be monocular (just one eye) or binocular (both eyes).

Question 2

what is the definiton of vertigo? [1]

what is vertigo caused by? [3]

what can it be divided into? [2]d

Answer 2

Vertigo: the false sensation that the body or environment is moving. The patient will either feel like they are moving, or the room is. Often it is a horizontal spinning sensation (similar to how you feel after turning in circles then stopping abruptly).

Vertigo is caused by a sensory mismatch between vision, proprioception and signals from the vestibular system

Vertigo can be divided into peripheral and central vertigo: peripheral vertigo are caused by problems with vestibular system, and central vertigo is caused by pathology affecting the brainstem/cerebellum or anything disrupting signalling input into here (i.e. tumour, posterior circulation stroke, etc)

Question 3

what is the definition of ataxia? [1]

what is ataxia caused by? [3]

how can ataxia present with regards to onset? [2]

Answer 3

Ataxia: this means the girl had problems with coordination, balance and speech. In this case, the ataxia is likely a result of the brain tumour found and structures it was compressing.

Ataxia is usually caused by cerebellar dysfunction or impaired vestibular or proprioceptive afferent input to the cerebellum.

Ataxia can have an insidious onset with a chronic and slowly progressive clinical course (eg, spinocerebellar ataxias [SCAs] of genetic origin) or have an acute onset, especially those ataxias resulting from cerebellar infarction, hemorrhage, or infection, which can have a rapid progression with catastrophic effects (the girl)

Question 4

what is the definiton of myopia? [1]

what is the definiton of astigmatism? [1]

what is the definiton of myopic astigmatism [1]

Answer 4

Myopia: This means near-sighted. Near-sightedness is a refractive error where the eyes see well at near distance, but struggle seeing further away.

Astigmatism: The eye is oval in shape. Normally, the surface of the cornea is perfectly round, yet some peoples are shaped less round à astigmatism. It is easily fixed using glasses or surgery.

Astigmatism occurs when the cornea or lens is curved more steeply in one direction than in another. You have corneal astigmatism if your cornea has mismatched curves. You have lenticular astigmatism if your lens has mismatched curves. In a perfectly shaped eye, each of these elements has a round curvature, like the surface of a smooth ball. A cornea or lens with such curvature bends (refracts) all incoming light equally to make a sharply focused image directly on the retina at the back of the eye.

Myopic astigmatism is basically meaning the 10 year old girl is near sighted (i_.e. can’t see objects far away that well)_ and has an astigmatism (her eyes are more oval than round shaped). These will be corrected via optometry, and she likely wears glasses that correct both these errors

Question 5

what is an antiacid? [1]

Answer 5

Antacid: medicines that counteract/neutralise the acid in your stomach to relieve indigestion and heartburn. Typically come as liquid or chewable tablets. A common example is Gaviscon, which is both an antacid and alginate.

Gastric acid-neutralizing agent; reacts with excess acid in the stomach, reducing acidity

Question 6

what is papilledema? [1]

how would you detect? [1]

Answer 6

Papilledema: optic disc swelling that is caused by increasing intracranial pressure. It is almost always bilateral, and cases by space-occupying lesions (i.e. tumours, haemorrhage).

fundoscopy detects

Question 7

what is estropria? [1]

what is Ptosis? [1]

Answer 7

Esotropia: This is when the eyes turn inwards (cross-eyed). Ocular alingmen tlike this can develop from many sources: congenital cross-eyes. Crossed eyes can also occur acutely, after a stroke or cranial nerve palsy

Ptosis: drooping of the upper eyelid due to paralysis or disease

Question 8

what is a brain tumour? [1]

Answer 8

The term brain tumour refers to an intracranial tumour affecting the brain, meninges, pituitary gland, pineal gland, cranial nerves and/or skull.

Question 9

medulloblastoma: arises from which cells in the brain? where does this occur? [1]

why is medulloblastoma highly metastatic? [1]

Answer 9

It is thought to arise from cerebellar stem cells between the brainstem and cerebellum near the fourth ventricle from the cerebellar vermis

Medulloblastoma tends to seed within CSF pathways giving rise to its high metastatic propensity

Question 10

describe 4 symptoms of medullablastoma [4]

Answer 10

Hydrocephalus: worsening headaches and decreased level of consciousness

Cerebellar signs: incoordination of limbs, gait abnormalities

Mass effect symptoms: speech and vision abnormalities, unilateral weakness, headache, drowsiness and nausea/vomiting

Extraocular muscle palsies: typically presents as diplopia

Question 11

what investigations would you do for medulloblastoma? [3]

Answer 11

Relevant investigations include:

Lumbar puncture (LP): performed post-operatively and useful for staging

MRI +/- CT including spinal imaging

histoligcal biopsy !

Question 12

what are management options for medullablastoma? [3]

Answer 12

Management options for medulloblastoma include:

Surgical removal of the tumour

Radiotherapy

Chemotherapy

Question 13

describe the pathophysiology of medullablastoma:

• arises from which cells[1] which part of brain? [1]
• medullablastoma can be cateogorised as? [4]
• Gene expression profiling has demonstrated that medulloblastoma is a group of diseases, and it has been categorised into four molecular groups, what are they? [4]
• there is strong evidence that mplication of which gene is associated with poor outcome? [1]

Answer 13

Medulloblastoma refers to a tumour of primitive neuroepithelial cells of the cerebellum. These tumours correspond to World Health Organization grade IV. Medulloblastoma may be categorised as desmoplastic, classic, large-cell, anaplastic, and variants with extensive nodularity, with myogenic and with melanotic differentiation. There is some evidence that children with large-cell and diffuse anaplastic variants have a worse prognosis.

Gene expression profiling has demonstrated that medulloblastoma is a group of diseases, and it has been categorised into four molecular groups: wingless (WNT), sonic hedgehog (SHH), and two additional groups called group 3 and 4.[15] [16] Patients whose tumours show WNT pathway activation usually have an excellent prognosis, while patients with SHH pathway-activated tumours generally have an intermediate prognosis. Outcome for the remaining patients is less favourable than that for patients with WNT pathway activation.

subtype 1 – wingless (WNT) medulloblastoma
subtype 2 – sonic hedgehog (SHH) medulloblastoma
subtype 2 – group 3 medulloblastoma
subtype 4 – group 4 medulloblastoma

There is strong evidence that amplification of the MYC oncogene (n-myc or cmyc), and deletions of chromosome 17p, are associated with poor outcome

Question 14

part of the brain does medullablastoma arise from? [1]
which structure does this block? [1] / how does it cause hydrocephalus? [1]

what can this cause in infants? [1]

Answer 14

Medulloblastoma arises from the vermis of the cerebellum and fills the fourth ventricle, blocking the outflow of cerebrospinal fluid.

The result is raised intracranial pressure due to obstructive hydrocephalus that causes headaches, nausea, impaired upward gaze, vomiting that often relieves the headache, and sixth cranial nerve palsies (e.g., impaired horizontal gaze and diplopia). In infants, the hydrocephalus can cause a rapid growth in head circumference and a bulging anterior fontanelle.[23] Other symptoms result from the mass effect exerted on the cerebellum, and include truncal and appendicular ataxia, nystagmus, a wide-based gait, and head tilt.

Question 15

name the 4 subtypes of medullablastoma

Answer 15

• Subtype 1 - wingless (WNT) medulloblastoma
• Subtype 2 - sonic hedgehog (SHH) medulloblastoma
• Subtype 3 - group 3 medulloblastoma
• Subtype 4 - group 4 medulloblastoma.

Question 16

medullablastoma is characterised by mutations in which gene? [1]

Answer 16

It is characterized by germ line mutations of the PTCH gene (which encodes for a transmembrane protein capable of binding the Hedgehog (HH) family of signaling proteins)

Question 17

what is hydrocephalus? [1]
hydrocephalus can broadly be divided into two categories, name and explain what they are they [2]

Answer 17

Hydrocephalus: Condition in which there is an excessive volume of CSF within the ventricular system, either caused by an imbalance between CSF production and absorption. Symptoms are due to raised ICP: headache (worse in morning, lying down), N+V, papilledema.

Hydrocephalus can be broadly divided into two categories: Obstructive (‘non-communicating’) hydrocephalus, Non-obstructive (‘communicating’) hydrocephalus:

Obstructive hydrocephalus is due to a structural pathology blocking the flow of cerebrospinal fluid. Dilatation of the ventricular system is seen superior to site of obstruction. Causes include: tumours, acute haemorrhage (e.g. subarachnoid haemorrhage or intraventricular haemorrhage) and developmental abnormalities (e.g. aqueduct stenosis).

Non-obstructive hydrocephalus is due to an _imbalance of CSF production absorptio_n. It is either caused by an increased production of CSF (e.g. choroid plexus tumour (very rare)) or more commonly a failure of reabsorption at the arachnoid granulations (e.g. meningitis or post-haemorrhagic).

Question 18

what is a ventriculo-peritoneal shunt?

Answer 18

Ventriculo-peritoneal shunt: long-term CSF diversion technique that drains CSF from ventricle to peritoneum

Question 19

define the following:

Mutism [1]

Paresis [1]

Anorexia [1]

Posterior fossa syndrome [1]

Answer 19

Mutism: absence of speech while conserving or maintaining the ability to hear others

Paresis: a condition of muscular weakness caused by nerve damage or disease;

Anorexia: lack or loss of appetit

Posterior fossa syndrome: also known as cerebellar mutism syndrome. Collection of neurological symptoms that occur following surgical resection of a posterior fossa tumour: characterised either by reduction in speech / absence of speech

Question 20

what is normal ICP in adults in supine? [1]

what is cerebral perfusion pressure? [1]

how do you calculate CPP? [1]

Answer 20

the normal ICP is 7-15 mmHg in adults in the supine position

cerebral perfusion pressure (CPP) is the net pressure gradient causing cerebral blood flow to the brain

CPP = mean arterial pressure - ICP

Question 21

describe the circulation of CSF in the brain

Answer 21

1. Lateral ventricles (via foramen of Munro)
2. 3rd ventricle
3. Cerebral aqueduct (aqueduct of Sylvius)
4. 4th ventricle (via foramina of Magendie and Luschka)
5. Subarachnoid space
6. Reabsorbed into the venous system via arachnoid granulations into **superior sagittal sinus
7. kept in motion by stereocilia of ependymal cells**

Question 22

what is the composition of CSF? [4]

what is the usual pressure - sitting & lying down? [2]

pH? [1]

Answer 22

Composition

Glucose: 50-80mg/dl
Protein: 15-40 mg/dl
Red blood cells: Nil
White blood cells: 0-3 cells/ mm3

Pressure

sitting: 7-15 mmHg
supine: 16-24 mmHg

pH
7.33

Question 23

The CSF fills the space between the …… mater and …. mater (covering surface of the brain).

The total volume of CSF in the brain is approximately ….ml.

Approximately 500 ml is produced by the …. cells in the …. …. (70%), or … … (30%). It is reabsorbed via the …. …. which project into the … …..

Answer 23

The CSF fills the space between the arachnoid mater and pia mater (covering surface of the brain). The total volume of CSF in the brain is approximately 150ml. Approximately 500 ml is produced by the ependymal cells in the choroid plexus (70%), or blood vessels (30%). It is reabsorbed via the arachnoid granulations which project into the venous sinuses.

Question 24

what is histology of medullablastoma like?

Answer 24

• Histology: Small, blue cells. Rosette pattern of cells with many mitotic figures

Question 25

medullablastom is infratentorial - what does this mean?

Answer 25

In anatomy, the infratentorial region of the brain is the area located below the tentorium cerebelli. The area of the brain above the tentorium cerebelli is

Question 26

what is the process of mestastasis of medullablastoma called? [1] how does it occur? [1]

what are homer-wright rosettes of medullablastomas? [1]

Answer 26

drop metastasis: travels via CSF to base of the spine; therefore grade 4

what are homer-wright rosettes of medullablastomas? [1]
dense tangles of neurones and neuroglial cells in ringlike structures formed by tumour cells

Question 27

PFS is characterised by either WHAT? [1]

Answer 27

PFS is characterised by either a reduction or an absence of speech.

Question 28

what are the onset of symptoms like for posterior fossa syndrome?

Answer 28

The onset of symptoms is generally within one week of surgery, manifesting in the first one to two postoperative days. Gross mutism is normally transient, lasting from one day to six months (5,11,12). However, cognitive, neurobehavioral and associated symptoms often persist for longer periods. Other associated symptoms include visual impairment, altered mood, impaired swallowing and significant gross and fine motor deficits.

Question 29

which muscles act to open the eyelid? [2]

Answer 29

The levator palpebrae superioris and superior tarsal muscles both act to open the eyelid. They are only present in the upper eyelid.

Question 30

describe how visual field worksx (from eye entering –> occipital)

Answer 30

The photoreceptors (rods and cones) in the retina are stimulated by photons of light entering the eye. Light-sensitive surface membrane proteins (e.g. rhodopsin) of these cells are stimulated to propagate second messenger responses which convert light energy into electrical signals. The photoreceptors synapse with retinal bipolar cells, which in turn transmit these signals to retinal ganglion cells.

The retinal ganglion cells converge at the optic disc, forming the optic nerve. The optic nerve then exits the eye, travelling through a defect in the lamina cribrosa of the sclera.

The optic nerve is the second cranial nerve, responsible for transmitting the special sensory information for vision. It may be considered an extension of the forebrain as it is covered by the meninges of the central nervous system, rather than by epi/peri/endoneurium like other peripheral nerves.

The optic nerve travels through the bony orbit and enters the middle cranial fossa through the optic canal, a defect in the lesser wing of the sphenoid.

Once inside the skull, the optic nerve travels along the floor of the middle cranial fossa, through the medial aspect of the cavernous sinus. Left and right optic nerves then converge at the optic chiasm.

The optic chiasm is located directly above the sella turcica of the sphenoid bone. The pituitary gland projects down immediately behind the chiasm.

At the chiasm, fibres from the nasal aspect of each retina cross over (or decussate) to the contralateral optic tract, while fibres from the temporal retina remain on their respective sides, as illustrated in figure 2.

In this way, left-sided post-chiasmal fibres pertain to the right side of the visual field, and vice versa.

The optic tracts extend from the chiasm to the thalamus. Here, afferent sensory nerves from the eye synapse with the second-order sensory neurones at the lateral geniculate nucleus in the thalamus. From here, the sensory nerves radiate dorsally to the calcarine sulcus of the occipital lobe.

Optic radiations loop either through the parietal lobe or through the temporal lobe (Meyer’s loop).

The optic radiations terminate in the calcarine sulcus of the occipital lobe, where the cortical visual centre is situated.

The calcarine sulcus is responsible for retinal image processing. Here, images from both eyes are finally collated and a final image is formed. This image is inverted, as represented in figure 1. As a consequence of this, the brain has to re-invert the image so that information is correctly oriented in space.

From the occipital visual centre, signals are sent to the frontal, parietal and temporal lobes to further make sense of the input information (e.g. reading/facial recognition).

Question 31

innervation to the muscles of the eyelid is via which nerves [3] to which muscles? [3]

Answer 31

• *facial nerve**: orbicularis oculi
• *oculomotor nerve**: levator palpebrae superioris
• *sympathetic fibres:** superior tarsal muscle

Question 32

The vestibular apparatus is located in the inner ear. It consists of three loops called the ….. ….. that are filled with a fluid called …..

These semicircular canals are oriented in different directions to detect various movements of the head. As the head turns, what happens? [1]

This fluid shift is detected …. found in a section of the canal called the …. . This sensory input of shifting fluid is transmitted to the brain by the …. nerve and lets the brain know that the head is moving in a particular direction.

Answer 32

The vestibular apparatus is located in the inner ear. It consists of three loops called the semicircular canals that are filled with a fluid called endolymph.

These semicircular canals are oriented in different directions to detect various movements of the head. As the head turns, the fluid shifts inside the canals.

This fluid shift is detected by tiny hairs called stereocilia found in a section of the canal called the ampulla. This sensory input of shifting fluid is transmitted to the brain by the vestibular nerve and lets the brain know that the head is moving in a particular direction.

Question 33

explain how the vestiublar nerve interacts with CN3, CN4 and CN6

Answer 33

The vestibular nerve carries signals from the vestibular apparatus to the vestibular nucleus in the brainstem and the cerebellum. The vestibular nucleus then sends signals to the oculomotor, trochlear and abducens nuclei that control eye movements and the thalamus, spinal cord and cerebellum.

The cerebellum is responsible for coordinating movement throughout the body. Therefore, the vestibular signals help the central nervous system coordinate eye movements and other movements throughout the body.

Question 34

Answer 34

Question 35

which special test could you conduct to assess vertigo?

Answer 35

Special tests that may be helpful in patients with dizziness or vertigo include:

Romberg’s test (screens for problems with proprioception or vestibular function)

Question 36

what causes binocular diplopia?

Answer 36

Binocular diplopia refers to double vision due to misalignment of the eyes, often caused by weakness or restricted movement of the muscles surrounding the eye (i.e., extraocular muscles)

Tumors may grow in areas of the brainstem affecting the eyes.

Question 37

what is esotropia?

Answer 37

Esotropia: inward positioned squint (affected eye towards the nose)

Question 38

what does CN3 palsy present as? [3]

Answer 38

Therefore when these muscles are no longer getting signals from the oculomotor nerve, the eyes moves outward and downward due to the effects of the lateral rectus and superior oblique still functioning without resistance.

It also supplies the levator palpebrae superioris, which is responsible for lifting the upper eyelid. Therefore third nerve palsy causes a ptosis.

The oculomotor nerve also contains parasympathetic fibres that innervate the sphincter muscle of the iris. Therefore third nerve palsy causes a dilated fixed pupil.

Question 39

Why can,cavernous sinus thrombosis and a posterior communicating artery aneurysm can cause compression of the nerve and a third nerve palsy?

Answer 39

The oculomotor nerve travels directly from the brainstem to the eye in a straight line. It travels through the cavernous sinus and close to the posterior communicating artery. Therefore, cavernous sinus thrombosis and a posterior communicating artery aneurysm can cause compression of the nerve and a third nerve palsy.

Question 40

functions of the superior oblique muscle? [3]

Answer 40

Abduction: when the muscle pulls toward the trochlea, it causes lateral deviation of the pupil and globe

Depression: the trochlea is located superiorly to the insertion of the superior oblique muscle, and pulling on the postero-lateral quadrant causes the globe to turn down

Intorsion: a combination of the abduction and depression movements is known as intorsion or medial rotation of the globe

Question 41

why does damage to CN VI cause horizontal diploplia?

Answer 41

Damage to either cranial nerve VI or the lateral rectus muscle will cause horizontal diplopia – double vision with images side-by-side. This is because the partial or complete palsy or weakness of the lateral rectus allows an unopposed pull of the medial rectus muscle in the same eye, pulling the visual axis medially.

Question 42

The treatment your child has after surgery depends on a number of factors. These include what?

Answer 42

The treatment your child has after surgery depends on a number of factors. These include:

• what the cells look like under the microscope – the type of medulloblastoma
• if the medulloblastoma has spread
• how old your child is

Based on these factors, your child goes into one of two treatment groups. These are based on the risk of medulloblastoma coming back after treatment. These groups are:

high risk
standard risk

High risk:

Your child only needs one of these factors to be in the high risk group:

• they are under 3 years old
• they have medulloblastoma that has spread
• their surgeon was not able to remove all of the tumour and the tumour that is left is more than 1.5cm in size
• they have large cell or anaplastic medulloblastoma
• they have certain gene changes

Standard risk

Every child in the standard risk group is 3 years or over. Their surgeon was able to remove all of their tumour, or they only have a very small amount left. Their medulloblastoma has not spread.

Question 43

What fibres branch off the main optic tracts instead of synapsing on the LGN of hypothalamus? [2]

Answer 43

Ans: fibres also branch into the superior colliculus of the midbrain to mediate visual reflexes via the extrinsic ocular muscles

and into the pretectal nucleus to mediate the papillary light reflex

Question 44

what expect from palsies of

CN3 [3]
CN4 [1]
CN6 [1]

Answer 44

Oculomotor: down and out (hypotropia and exotropia) due to dominance of the remaining extraocular muscles; in addition you would expect ptosis and mydriasis (eyelid drooping and dilated pupils)

Trochlear: _double vision, trouble looking dow_n (fall risk down stairs!)

Abducens: adduction

Question 45

•What penetrates the 3rd ventricle and connects both lateral walls? [1]

Answer 45

6. The interthalamic adhesion

Question 46

•what risks are associated with RT?

Answer 46

Ans: Radiotherapy has serious adverse effects on the neurocognitive development of young children; the younger the child, the greater the deleterious effects. Attempts to avoid craniospinal radiation (by substituting focal radiation in infants) can result in a high rate of relapse.

Question 47

what is prognosis of meduullablastoma?

Answer 47

Prognosis

Five-year progression-free survival for standard-risk patients is approximately 79% to 83% but only 50% for high-risk patients

For infants, historical data suggests 5-year progression-free survival in the range of 20% to 40%

Question 49

explain what holistic care could be given to the patient? [3]

Answer 49

Physical therapy:

Physiotherapy helps to restore movement and function when someone is affected by injury, illness or disability. It can also help to reduce your risk of injury or illness in the future.

• *education and advice** – physiotherapists can give general advice about things that can affect your daily lives, such as posture and correct lifting or carrying techniques to help prevent injuries
• *movement, tailored exercise and physical activity advice –** exercises may be recommended to improve your general health and mobility, and to strengthen specific parts of your body
• *manual therapy –** where the physiotherapist uses their hands to help relieve pain and stiffness, and to encourage better movement of the body

Occupational therapy
Occupational therapy aims to improve your ability to do everyday tasks if you’re having difficulties.

providing comprehensive assessment
improving or maintaining functional levels
organising a safe home environment
facilitating discharge from hospital

Speech therapy

speech and language therapists provide life-changing treatment, support and care for children and adults who have difficulties with communication, eating, drinking and swallowing. You’ll help people who, for physical or psychological reasons, have problems speaking and communicating

Question 50

what is 4?

what is 6?

Answer 50

4 = caudate nuclei
6 internal capsule

Question 51

Why might antacids have helped with NV in this case?

How do they work?

Answer 51

Likely to be purely symptomatic relief – NV here is ‘neurogenic’

help neutralize stomach acid (and generally well tolerated by kids)

They also inhibit pepsin, which is an enzyme that plays a role in protein digestion. Pepsin works with hydrochloric acid in the stomach to provide the acidic environment necessary to digest food.

Some antacids include a foaming agent called alginate that floats on top of the stomach contents and prevents acid from coming into contact with the esophagus.

Question 53

What does Edinger-Westphal nucleus do? [3]

what does the pretectal nucleus do? [1]

Answer 53

The Edinger–Westphal nucleus supplies preganglionic parasympathetic fibers to the eye, constricting the pupil, accommodating the lens, and convergence of the eyes.

It forms the site of origin of the parasympathetic fibres that travel with the oculomotor nerve. The EWN lies immediately posterior and adjacent to the oculomotor nucleus, and its fibres encase the oculomotor fibres like a pipe.

CN II sends afferent light-sensing fibres to the pretectal nucleus of the midbrain. The pre-tectal nucleus then communicates to the EWN that there has been a change in light intensity, causing the pupils to constrict or dilate.

Question 54

how does CN3 cause lens accomodation and pupil contriction?

Answer 54

Ciliary muscles: contract, adapting to close-range vision with a more spherical lens

Constrictor pupillae: pupillary constriction to reduce the amount of light reaching the retina

Question 55

how does photoreception occur in light / dark?

Answer 55

So in essence when light triggers a photoreceptor, it turns off and stops releasing neurotransmitters (decreases the inward current of sodium entering the cell and the photoreceptor becomes more negative, or hyperpolarized).

As a result, there’s less of the excitatory neurotransmitter glutamate released into the synapse between the photoreceptor and bipolar cell.

Interestingly, it’s the lack of glutamate that causes the bipolar cell to open up its voltage-gated calcium channels and depolarize.

And the bipolar cell then triggers depolarization of the ganglion cell.

And from there, the action potential is propagated along the optic nerve and ultimately to the primary processing centers in the brain in the occipital lobe.