OHCEPS - The Nervous System Flashcards
Dizziness - Clarify what?
- Sense of rotation = vertigo.
- Swimminess or lightheadedness –> rather non specific symptom which can be related to pathology in many different systems.
- Pre-syncope –> rather unique feeling one gets just prior to fainting.
- Incoordination –> many will say they are dizzy when, in fact, they can’t walk straight due to either ataxia or weakness.
Headache?
Treat as any other pain + Ask about facial or visual symptoms.
Numbness and weakness?
- These two words are often confused by patients - Describing a leg as numb when it is weak with normal sensation.
- Also, patients may report “numbness” when, in fact, they are experiencing pins-and-needles or pain.
Tremor - Ask what?
- Here you should establish if the tremor occurs only at rest, only when attempting an action or both.
- Worse any particular time of the day.
- Severity can be established in terms of its functional consequence (can’t hold a cup/put food to mouth?).
- Again, establish EXACTLY what is being described. A tremor is a shaking, regular or jerky involuntary movement.
Falls and loss of consciousness (LOC) - Ask what?
- Eyewitness is vital.
- Establish also whether the patient actually lost consciousness or not.
- People often describe “blacking out” when in fact they simply fell to the ground –> Drop attacks have no LOC.
- Important question –> Can you remember hitting the ground?
Falls and LOC - Preceding symptoms?
They may point towards a different organ system:
- Sweating + Weakness could be a marker of hypoglycemia.
- Palpitations may indicate a cardiac dysrhythmia.
Seizures - Ask what?
- Impairment of consciousness + seek collateral histories.
- Lay persons usually consider seizure = fit = tonic clonic seizure.
- A surprising number of people also suffer “pseudoseizures” which are non-organic and have a psychological cause.
Seizures - History-taking - Few points to consider:
- Syncopal attacks can often cause a few tonic-clonic jerks which may be mistaken for epilepsy.
- True tonic-clonic seizures may cause tongue-biting, urinary and fecal incontinence, or ALL of the above.
- People presenting with pseudoseizure can have true epilepsy as well and vice versa.
Visual symptoms?
- Commonly visual loss, double-vision, or photophobia.
- Establish EXACTLY what is being experienced –> Diplopia is often complained of when, in fact, the vision is blurred or sight is generally poor (amblyopia) or clouded.
Rest of history - Remember to ask?
If the patient is right or left-handed –> consider disability from loss of function and may also be useful when thinking about cerebral lesions.
Rest of history - Direct questioning?
Enquire neurological symptoms OTHER than the presenting complaint:
- Headaches
- Fits
- Faints
- “Funny turns”
- Blackouts
- Visual symptoms
- Pins-and-needles
- Tingling
- Numbness
- Weakness
- Incontinence
- Constipation
- Urinary retention
PMH - Ask?
A birth history is important –> Particularly in epilepsy –> Brain injury at birth has neurological consequences.
- HTN - if so, what treatment?
- DM - type, treatment?
- Thyroid disease
- Mental illness (eg depression)
- Meningitis or encephalitis
- Head or spinal-injuries
- Epilepsy, convulsions, or seizures
- Cancers
- HIV/AIDS
DHx - Ask?
- Anticonvulsant therapy - current, previous.
- OCPs
- Steroids
- Anticoagulants or anti-platelet agents.
FHx - Ask?
Thoroughly –> Ask about neurological diagnoses and evidence of missed diagnoses (eg seizures, blackouts).
SHx - Ask?
- Occupation + Exposure to heavy metals or other neurotoxins.
- Driving? - Many neurological conditions have implications here.
- Ask about the home environment thoroughly - very useful when considering handicaps and consequences of the diagnosis.
- Ask about support systems - family, friends, home-helps, day centre visits etc.
Brief outline of neurological exam?
- Inspection, mood, conscious level.
- Speech and higher mental functions.
- Cranial nerves II-XII
- Motor system
- Sensation
- Co-ordination
- Gait
- Any extra tests
- Other relevant exams –> skull, spine, neck stiffness, ear drums, BP, anterior chest, carotid arteries, breasts, abdomen, lymph nodes.
General inspection and mental state?
- Are they accompanied by carers - how do they interact with those people.
- Do they use any walking aids?
- Any abnormal movements?
- Observe gait as they approach the clinic room.
- Any speech disturbance
- What is their mood like?
- Ask how they feel.
- State of clothing, hair, skin, nails?
- Restlessness, inappropriately high spirits, pressure of speech?
- Obviously depressed with disinterest?
- Denying any disability?
Speech and language - Exam?
- May be evident from the start - no formal testing required.
- Briefly test their language function by asking them to read or obey a simple written command (eg close your eyes) + write a short sentence.
- If apparently problematic, speech can be tested formally by asking the patient to respond to progressively harder questions… yes/no, simple statements, more complicated statements and finally tongue twisters.
- Before everything –> Ensure that the patient is NOT DEAF + They can usually understand English.
Dysarthria is?
A defect of articulation –> Language function is INTACT (writing will be unaffected).
Dysarthria - Lesion may be?
- Cerebellar lesion
- LMN lesion of the cranial nerves
- Extrapyramidal lesion
- Problem with muscles in the mouth and jaws or their nerve supply.
Dysarthria - Exam?
- Listen for slurring and the rhythm of speech.
- Test function of different structures by asking the patient to repeat “Yellow Lorry” or words with D, L, T –> Tongue function.
- Lip function –> Peter Piper picked a pickle.
Dysarthria - cerebellar lesions?
Slow, slurred, low volume with equal emphasis on all syllables (“scanning”).
Dysarthria - Facial weakness?
Speech is slurred.
Dysarthria - extrapyramidal lesions?
- Monotonous
- Low volume
- Lacking in normal rhythm
Dysphonia is?
Defective volume - huskiness,
Dysphonia - etiology?
- Laryngeal disease
- Laryngeal nerve palsy
- Rarely muscular disease such as myasthenia gravis.
- May also be psychological.
Dysphasia is?
Defect of language, NOT JUST SPEECH, so reading and writing may also be affected - some patients attempt to overcome speaking difficulties with a notepad and a pen only to be bitterly disappointed.
Global dysphasia?
Patient is unable to speak or understand speech at all.
Broca and Wernicke affected.
Expressive dysphasia?
- Lesion in Broca (frontal lobe) - involved in language production.
- Understanding remains intact.
- Unable to answer questions appropriately.
- Speech is non-fluent, broken with abnormal word ordering.
- Unable to repeat sentences.
Expressive dysphasia - other terms?
Anterior, motor, or Broca’s dysphasia.
Receptive dysphasia?
- Lesion in Wernicke - Problems understanding spoken or written language (dyslexia) and problems with word-finding.
- Unable to understand commands or questions.
- Speech is fluent with lots of meaningless grammatical elements.
- May contain meaningless words.
- Unable to repeat sentences.
- Patients are often unaware of their speech difficulty and will talk nonsense contentedly –> although may become frustrated with other people’s lack of understanding!!!
Other terms for receptive dysphasia?
Posterior, sensory, or Wernicke’s dysphasia.
Jargon dysphasia?
Describes a severe form of receptive dysphasia containing only meaningless words (neologisms) and sounds.
Paraphasia is?
The supplementation of one word with another.
Conductive dysphasia?
- Lesions in the arcuate fasciculus and/or other connections between the 2 primary language areas.
- Patient can comprehend and respond appropriately.
- Unable to REPEAT A SENTENCE.
Nominal dysphasia?
- All language function is intact EXCEPT for naming of objects.
- Caused by lesion in angular gyrus.
- Patient may function with “circumlocution” –> eg says “that thing that I write with” if unable to say “pen”.
Cognitive function - How to exam?
With the abbreviated mental test score (10 points).
What does the abbreviated mental test score include?
- Date of birth
- Age
- Time
- Year
- Place
- Head of state –> Who is the prime minister –> NAME is required.
- WWII –> What year did the WWII started?
- 5-minute recall –> Tell the patient an address (often 42 West street is used) and ask them 5min later to recall it.
- 20-1 –> Backward counting from 20 to 1.
- Recognition –> What job do I do? (doctor) and “What job does this man/woman do?” (nurse) –> BOTH must be correct to score a point.
CN I - Applied anatomy?
- Fibers arise in the mucous membrane of the nose.
- Axons pass across the cribriform plate to the olfactory bulb.
- Olfactory tract runs backwards below the frontal lobe + projects, mainly, in the uncus of the ipsilateral temporal lobe.
CN I - Applied anatomy - Interesting?
Olfactory epithelium also contains free nerve endings of the 1st division of CN V.
CN I - Casual exam?
Take a nearby odorous object (coffee, chocolate) and ask the patient if it smells normal.
CN I - Formal exam?
A series of identical bottles containing recognizable smells are used. The patient is asked to identify them.
Commonly used agents:
1. Coffee
2. Vanilla
3. Camphor
4. Vinegar
–> Test EACH nostril separately + determine if any loss of smell is uni- or bilateral.
Bilateral anosmia?
Usually NASAL, not neurological.
Bilateral anosmia - etiology?
- URI
- Trauma
- Smoking
- Old age
- Parkinson
- Less commonly tumors of the ethmoid bones or congenital ciliary dysmotility syndromes.
Unilateral anoma?
- Mucous-blocked nostril.
- Head trauma
- Subfrontal meningioma
CN I - Hints:
- Peppermint
- Ammonia
- Methanol
stimulate the FREE TRIGEMINAL ENDINGS so are not as a good test of CN I.
Only part of the CNS that can be directly visualized?
Optic nerve begins
Visual acuity - Formally tested with?
A Snellen’s chart.
Visual acuity - how to exam?
- In good light, the patient should stand 6m away from the chart.
- Each eye is tested in turn and the patient is asked to read the chart.
- The number above each line indicates the distance at which a person with normal sight should be able to read it.
- Record the line reached - allow max of 2 errors/per line.
- Indicate results as: distance from chart/distance it should be read eg 6/36.
Visual acuity - if the patient CAN’T see any of the letters, record whether they can?
- Count Fingers held in front of their face (CF)
- See hand movements (wave your hand).
- Perceive light –> CF, HM, PL, or NPL (not perceive light).
Color vision?
- Not tested routinely.
2. Tested using Ishihara plates.
Visual field - Normal?
The area that the eye can see without moving is NOT CIRCULAR –> Eyebrows and nose obstruct superiorly and nasally whereas there is no obstruction laterally.
Gross defects and visual neglect (inattention)?
- Sit opposite the patient, 1m, eyes levels.
- Test first for gross defects + visual neglect with both eyes open.
- Raise your arms up to the sides so that one hand is in the upper right quadrant of your vision and one in the upper left.
- Ask patient to look directly at you (“look at my nose”).
- Move one index finger and ask the patient, while looking straight at you, to point to the hand which is moving.
- Test with the right, left, and with both hands.
- Test the lower quadrants in the same way.
- If VISUAL NEGLECT is present –> patient will be able to see each hand moving individually but reports seeing only one hand when BOTH are moving.
Test the eyes - if the patient is unable to cooperate?
- Like much of the neurological exam, gross defects can be seen without the patient’s cooperation (confused or drowsy).
- Test for response to “menace” by bringing your hand in sharply from the side, stopping just short of hitting the patient in the eye.
- If your hand can be seen, the patient will BLINK.
- Test vision on the left and the right side.
Tunnel vision?
Confusing term –> Constricted visual field, giving the impression of looking down a pipe or tunnel.
Tunnel vision - etiology?
- Glaucoma
- Retinal damage
- Papilledema
- Often “functional”
Enlarged blind spot?
Caused by papilledema.
Unilateral field loss?
Blindness in one eye caused by devastating damage to the eye, its blood supply, or optic nerve.
Central scotoma?
A hole in the visual field (macular degeneration, vascular lesion or, if bilateral, toxins).
If bilateral may indicate a very small defect in the corresponding area of the occipital cortex (MS) !!!
Bitemporal hemianopia?
Nasal half of BOTH retinas, and therefore, the temporal half of each visual field is lost (damage to the center of the optic chiasm such as a pituitary tumor, craniopharyngioma, suprasellar meningioma).
Binasal hemiaponia?
The nasal half of each visual field is lost (very rare).
Homonymous hemianopia?
- May be left or right.
- Commonly seen in stroke patients
- Right OR Left side in both eyes is lost.
- If the macula is spared –> lesion in the optic radiation.
- If the macula is NOT spared –> lesion in the optic tract.
Homonymous quadrantanopia?
Corresponding quarters of the vision is lost in each eye .
Upper quadrantanopias suggest?
Lesion in TEMPORAL LOBE.
Lower quadrantanopias suggest?
Lesion in the parietal lobe.
For a complete ophthalmoscopic exam do what?
It is often worth dilating the pupil by instilling a few drops of mydriatic - 1% tropicamide or 1% cyclopentolate - into the inferior conjunctival sac.
With a little practise one often finds that this is not necessary for a routine exam.
If you plan to dilate the pupil, ask what?
If they have a history of angle closure glaucoma or episodes of seeing haloes around lights at night-time.
Ophthalmoscopy - Exam steps?
- Performed in a dimly lit room.
- Ask patient to focus on distant object + keep eyes still.
- Look through the ophthalmoscope (OS) 30cm away from the patient and bring the light in nasally from the temporal field to land on the pupil.
- Dial up a hypermetropic (plus) lens on the OS to focus on the corneal surface + move in as close as possible to the patient’s eye –> By gradually decr. the power of lens –> examine cornea, iris, and lens in turn.
- Continue to decr. power of the lens until you can sharply focus on the retinal vessels.
- It is often best to pick up one of the vascular arcades in the periphery and track them in towards the optic disc.
- Take time to look carefully - esp. where the arteries cross veins.
- Ask the patient to look directly into the light of the OS to gain a view of the vascular region.
Normal fundus - The optic disc?
- Healthy disc is pale pink/yellow and round or slightly oval in shape.
- Margins between disc and surrounding retina should be crisp and well defined –> Occasionally a surrounding ring is present which may be slightly lighter or darker in color.
- At the centre of the disc is the physiological cup. It appears paler in color compared to the rest of the disc.
Normal fundus - The macular region?
- Located temporally from the optic disc.
- This is the region with the maximum concentration of cones.
- At the centre of the macula is the fovea –> tiny pit DEVOID OF BLOOD VESSELS and responsible for fine resolution.
- Disease involving the macula and fovea can cause devastating visual loss.
Normal fundus - The retinal vessels?
- The central retinal artery/vein enter and leave the globe in the center of the optic disc.
- Veins appear larger and darker in color in comparison to the arteries.
- Spontaneous venous pulsations are seen in many normal eyes.
- Arterial pulsations should NOT be visible in normal eyes.
Ophthalmoscopy - Hint?
View the macula by directing the light on the most sensitive part of the eye. This can often be unpleasant for the patient and will lead to more marked miosis and a restricted view.
Abnormal findings on fundoscopy - Optic disc swelling - Appearance?
- Raised, swollen, enlarged.
- Disc often appears darker in color
- Margins of the disc are blurred and become indistinct from the adjacent retina.
- Retinal vessels can be seen arching down from the raised disc towards the peripheral retina.
- In severe cases –> Retinal hemorrhage may be seen around the disc.
What does papilledema mean?
Swelling of the optic disc due to INCR. INTRACRANIAL PRESSURE.
Not all optic disc swelling is papilledema.
Optic disc swelling - etiology?
- Space occupying lesions –> Malignancy, subdural hematoma, cerebral abscess.
- Subarachnoid hemorrhage –> Commonly associated with vitrous hemorrhage.
- Chronic meningitis
- Idiopathic intracranial HTN
- Malignant HTN
- Ischemic optic atrophy
Optic disc cupping - appearance?
- Physiological cup is incr. in respect to the rest of the disc.
- Retinal vessels kink sharply as they emerge over the rim of the cup.
- Hemorrhages may be present.
Optic disc cupping - Etiology?
Most commonly one of the various types of glaucoma.
Optic atrophy - Appearance?
Pale optic disc due to loss of nerve fibers in the optic nerve head.
Optic atrophy - Etiology?
- Ischemic optic neuropathy
- Optic neuritis
- Trauma
- Optic nerve compression
Retinal hemorrhage - Appearance?
- Depends on its location within the various layers of the retina.
- Deep hemorrhages appear as “dots” due to the close packing of the cells in this region.
- More superficial hemorrhages in the nerve fiber layer appear as more widespread “blotches”.
Retinal hemorrhages - Etiology?
- DM
- HTN
- Subarachnoid hemorrhage
- Blood dyscrasias
- Systemic vasculitis
- Valsalva maneuver
- Trauma
- Bacterial endocarditis (known specifically as Roth spots)
Central/branch retinal artery occlusion - Appearance?
- Large areas of ischemic white retina associated with sudden catastrophic visual loss.
- Calcific, cholesterol or fibrin-platelet emboli can often be seen occluding the retina artery/branch.
Central/branch retinal artery occlusion - etiology?
Either embolic or thrombotic (remember giant cell arteritis also).
Central/branch retinal VEIN occlusion - appearance?
- Large, widespread flame-shaped hemorrhages –> stormy sunset.
- Gradual onset painless blurred vision and visual loss.
- Optic disc swelling may be present.
Central/branch retinal VEIN occlusion - etiology?
- Blood dyscrasias
- DM
- Glaucoma
Foster-Kennedy syndrome - appearance?
- UNILATERAL optic atrophy
- Contralateral papilledema
- Central scotoma
- Anosmia (variable)
- Systemic symptoms –> Headache, dizziness, vertigo, vomiting.
Foster-Kennedy syndrome - etiology?
- Meningioma of optic nerve, olfactory groove or sphenoid wing.
- Frontal lobe tumor.
Variation in the pupil size is brought about by 2 muscles in the iris under ANS?
- Sphincter pupillae muscle
2. Dilator pupillae muscle
Sphincter pupillae muscle?
Found in the iris at the margin of the pupil.
Innervated by PNS fibers –> Constricts the pupil (miosis).
Dilator pupillae muscle?
Radially arranged smooth muscle –> Innervated by SNS –> Dilates pupil (Mydriasis).
Pupillary light response - mechanism?
- Afferent fibers leave the eye in the optic nerve and separate in the midbrain to synapse with the 3rd nerve nuclei.
- Efferent pathway fibers then travel to synapse in the ciliary ganglion before innervating the sphincter pupillae.
Pupil - examination?
- Inspect both pupils in good light - is there a discrepancy in size (anisocoria) or shape? –> Present in 25% of normal population.
- May be secondary to previous ocular inflammation disease, trauma, or surgery.
If anisocoria is present?
Must determine which of the pupils is the correct size:
- Pathologically constricted pupil is more obvious in dim light as the normal pupil dilates.
- A pathologically large pupil will be more apparent n bright illumination when the normal pupil will constrict.
Marcus-Gunn swinging light test?
Assess the AFFERENT limb of the pupillary light pathway:
- Shine light in the normal eye and both pupils constrict –> consensual response in the affected eye is intact.
- Swing the light to the affected eye and both pupils dilate –> afferent drive to cause constriction of the pupils from the affected eye is reduced in comparison to that of the unaffected eye.
- Swing the light back to the normal eye and both pupils constrict.
Exam the EFFERENT limb of the pupil reflex?
Ask the patient to focus on a distant object and then look immediately to your index finger held 30cm in front of their face.
–> normal will be for the pupils to constrict in response to convergence and accommodation.
Argyll-Robertson pupil?
- Midbrain lesions caused by neurosyphilis target the more dorsally located fibers that subserve the light response.
- Ventrally located fibers responsible for accommodation are spared.
Argyll-Robertson pupil - appearance?
Small irregular pupil that accommodates but does NOT react to light.
Argyll-Robertson pupil - causes?
- Neurosyphilis
2. DM
Holmes-Adie pupil?
- Denervation of the Iris and ciliary body due to ciliary ganglionitis (although some would dispute this!).
- Associated loss of tendon reflexes is seen in some patients and is termed Holmes-Adie syndrome.
Holmes-Adie pupil - appearance?
Unilateral dilated pupil –> Accommodates and relaxes very slowly and shows absent or depressed light reflex –> Supersensitive to 0.1% pilocarpine (causing constriction).
Holmes-Adie pupil - etiology?
- Usually IDIOPATHIC and predominates in young adult females (2:1).
- May also follow iridoplegia or ocular trauma.
Horner’s syndrome - appearance?
- Unilateral miotic pupil with partial Ptosis (due to paralysis of Muller’s muscle - a small smooth muscle in the upper lid.
- Movement of the upper lid should be intact as the levator muscle is supplied by the oculomotor nerve.
- Variable interruption of sudomotor innervation to the ipsilateral side of the face.
- Sweating is absent if the lesion occurs proximal to the carotid plexus, after which the sudomotor fibers separate.
Horner’s syndrome - etiology?
- Protracted course of the sympathetic pathway makes it vulnerable to disruption at many different points.
- Congenital - often associated with an alternation in Iris pigment (heterochromia).
- Injury or surgery to the neck.
- Multiple sclerosis
- Cevernous sinus disease
- Neoplasia involving the mediastinum, cervical cord or the apex of the lung.
- Infarction - secondary to occlusion of the basilar or posterior inferior cerebellar artery.
- Thoracic aortic aneurysm
- Syringomyelia or syringobulbia
What is Klumpke’s paralysis?
Avulsion of the C8 and T1 roots.
Oculomotor - motor innervation?
- Levator palpebrae superioris
- Superior rectus
- Medial rectus
- Inferior rectus
- Inferior oblique
Oculomotor - autonomic?
PNS supply to the constrictor (sphincter) pupillae of the Iris and ciliary muscle.
Main oculomotor nucleus?
Lies anterior to the aqueduct of the midbrain.
Edinger-Westphal nucleus?
Accessory PNS nucleus –> Lies posterior to the oculomotor nucleus.
Fibers pass anteriorly, through the cavernous sinus, entering the orbit through the superior orbital fissure.
Trochlear - motor?
Superior oblique
Trochlear nucleus?
- Lies Inferiorly to that of the oculomotor and has connections with the cerebral hemispheres, visual cortex and nerves III, VI, VIII.
- Fibers pass POSTERIORLY and immediately crooks one another.
- They then travel through the cavernous sinus, entering the orbit through the superior orbital fissure.
Abducens - nucleus?
- Lies beneath the 4th ventricle.
- Connects with the nuclei of the III and IV through MLF.
- Emerges from the pons and travels through the cavernous sinus to enter the orbit through the superior orbital fissure.
Examination of III, IV, VI?
- Inspect position of the lids –> Epicanthic folds prominent? Ptosis?
- Look at the position of the eyes in neutral gaze.
- Asymmetrical position suggests strabismus (squint) and this should be assessed with the cover test.
- Ask patient to follow your index finger in vertical, horizontal, and oblique planes - avoiding extremes of gaze.
- Is nystagmus present?
- Diplopia? Ask the patient.
- Eyes should follow smoothly the moving target (pursuit) –> often interrupted with saccades in Parkinson/Huntington.
How to test saccadic eye movements?
- Now hold up your index finger on one side of their head and your thumb on the other - in their temporal visual fields.
- Ask the patient to look quickly between finger and thumb –> Should be accurate, smooth, rapid.
How to test convergence?
Ask the patient to look from a distant object to a near object –> the eyes should converge smoothly and equally in association with accommodation and pupil constriction.
Ptosis (dropping of the lid) - Causes?
- Weakness of the levator muscle in myasthenia gravis.
- CN III palsy
- Disruption of the insertion of the levator muscle into the tarsal plate of the lid either through surgery or trauma.
Strabismus/squint - Divergent?
One eye is directed towards the target, the other is turned laterally.
Strabismus/squint - Convergent?
The other eye is turned medially.
2 forms of squint?
- Non paralytic
2. Paralytic
Non paralytic squint?
- Seen in childhood
2. Both eyes have a full range of movement but only one of the eyes is directed towards the target of fixation.
Paralytic squint
Movement of one or more of the extraocular muscles is decreased due to disease of the muscle, a nerve palsy, or a physical obstruction to movement in a particular direction –> tethering, trauma, or neoplasm.
The cover-uncover test
Used for further analysis of non-paralytic squint:
1. Patient sits in front of you.
2. Present a fixation target in front of them (top of your pen for example).
3. Ask them to cover their right eye.
4. Closely observe the uncovered left eye –> One of three is possible:
a. Eye doesn’t move at all –> normal.
b. Eye moves nasally to fixate –> Divergent squint
c. Eye moves temporally to fixate –> Convergent squit
Repeat covering the left eye.
More sophisticated assessment of squint?
Using a syntophore in eye clinics.
Further assessment of squint?
Should always involve a detailed assessment of the cornea, lens, vitreous and retina to exclude opacities and abnormalities.
Nystagmus is?
Oscillating movements of the eyes.
Vestibular nystagmus?
Type of jerk nystagmus (to and fro movements are of different velocities).
Vestibular nystagmus - Etiology?
Caused by disease in the labyrinth or its central connections.
Vestibular nystagmus - fast phase?
Is away from the side of the lesion.
Vestibular nystagmus - features?
- Often horizontal and rotatory components.
2. Usually only present in the acute phase of labyrinthine disease.
Pendular nystagmus?
- The velocity of the movements is the same in BOTH directions.
- Often a congenital condition associated with deceased visual acuity.
Pendular nystagmus - seen in?
- Cerebrovascular disease
2. Multiple sclerosis
Oscillopsia?
Patients with acquired nystagmus will often complain of continual movement of their visual environment, which is NOT the case with congenital nystagmus.
Optokinetic nystagmus?
This is a normal response of the eye when trying to follow a moving object - when looking from the window of a train.
Defective optokinetic nystagmus seen in?
Lesions of the deep parietal lobe when drum rotation is towards the affected hemisphere.
Upbeat nystagmus?
The fast phase is upwards.
Upbeat nystagmus - etiology?
- Brainstem disease
2. Intoxication with alcohol and a number of other drugs including phenytoin.
Downbeat nystagmus?
The fast phase is downwards.
Downbeat nystagmus - seen in?
- In toxic states and Demyelinating diseases.
2. Herniation of cerebellar tissue through the Foramen magnum as seen in Chiari malformation.
Gaze-evoked nystagmus?
The fast phase is towards the direction of action of the affected muscle.
Gaze-evoked nystagmus - seen in?
In dysfunction of extraocular muscles secondary to intrinsic weakness or nerve palsy.
Hint about nystagmus exam?
When assessing nystagmus try to avoid the extremes of lateral gaze (I.e. Not >30 degrees) –> This will elicit end-point nystagmus - a physiological response not to be confused with a pathological process.
Oculomotor palsy - Appearance?
- Pupil dilated and response to neither light nor accommodation.
- All the extraocular muscles are paralyzed except for the lateral rectus and the superior oblique.
- Unopposed action of these cause the eye to look DOWN AND OUT.
Paralysis of the levator palpebrae muscle causes?
COMPLETE ptosis.
Oculomotor palsy - etiology?
- DM (pupil sparing)
- Lesions involving the superior orbital fissure.
- Cavernous sinus disease
- Aneurysm of posterior communicating artery
- Weber syndrome (associated CONTRALATERAL hemiplegia)
Palsy of trochlear nerve - appearance?
- Paralysis of the superior oblique causes the eye to elevate when adducting.
- Patient complains of Diplopia and will have difficulty looking downwards and inwards on the affected side.
- Patient may try to compensate for this by tilting their head away from the side of the lesion –> Ocular torticollis.
Causes of trochlear nerve palsy?
- Trauma
- Surgery
- DM
- Atherosclerosis
- Neoplasia
Abducens palsy - appearance?
- Paralysis of the lateral rectus muscle means the eye cannot be abducted from the midline and the unopposed action of the medial rectus leaves the eye deviated NASALLY at rest.
- Patient complains of Diplopia in horizontal gaze.
- Lesions in the 6th nerve nucleus also involve the lateral gaze centre and lead to gaze paresis.
Abducens nerve palsy - Etiology?
- DM
- Atherosclerosis
- MS
- Neoplastic lesions
- Raised intracranial pressure leading to compression of the nerve on the edge of the petrous temporal bone (a false localizing sign).
- Trauma
- Surgery
Combined nerve palsies - The cavernous sinus?
All 3 nerves involved in Oculomotor control along with sympathetic fibers to the Iris and the ophthalmic and maxillary divisions of the trigeminal nerve pass through here.
Common lesions of the cavernous sinus?
- Carotid-cavernous fistula
- Expanding pituitary tumor
- Cavernous sinus thrombosis - associated with proptosis and injection of conjunctival vessels (chemosis)
- Aneurysm
Combined nerve palsies - The orbit?
- A complex range of Ophthalmoplegias can result from any compressive lesion located within the orbit.
- Proptosis may be present with variable optic nerve involvement.
- Many lesions may directly impinge upon the extraocular muscles as well as the innervating nerves.
Combined nerve palsies - Superior orbital fissure?
- Transmits all the nerves supplying the extraocular muscles along with the ophthalmic division of the trigeminal nerve.
- Inflammation or a lesion at the superior orbital fissure leads to Tolosa-Hunt syndrome.
Tolosa-Hunt syndrome?
A complex unilateral ophthalmoplegia associated with anesthesia over the forehead and ocular pain.
Internuclear ophthalmoplegia of III, IV, VI?
This is interruption of the MLF, connecting the nuclei of cranial nerves III and VI on opposite sides.
Internuclear ophthalmoplegia of III, IV, VI - Appearance?
- Impaired adduction in the IPSILATERAL eye in unilateral lesions -nystagmus is often seen in the abducting eye.
- Bilateral lesions often cause vertical nystagmus and impaired vertical pursuit.
- Convergence remains intact.
- Patient will complain of horizontal Diplopia due to impaired adduction on the affected side - not due to nystagmus in the abducting eye.
Internuclear ophthalmoplegia III, IV, VI - Etiology?
- Cerebrovascular disease
2. Multiple sclerosis.
Lesions of the parapontine reticular formation?
The PPRF is responsible for conjugate eye movements in horizontal gaze.
Lesions of the PPRF - Appearance?
- Failure of horizontal eye movements towards the side of the lesion - Horizontal gaze paresis.
- An ipsilateral Internuclear ophthalmoplegia if the lesion extends to involve the MLF.
- Preservation of vertical gaze.
- Contralateral deviation of the eyes in the acute phase.
Lesions of the parapontine reticular formation?
- Vascular disease
- Demyelinating disease
- Neoplasia
Parinaud’s syndrome?
Lesions occurring in the dorsal midbrain involve the vertical gaze centre - hence also known as dorsal midbrain syndrome.
Parinaud’s syndrome - Appearance?
- Impaired upward gaze in both eyes resulting in convergence, retraction of the globe into the orbit and nystagmus.
- Light-near dissociation of the pupils - The near reflex is intact but response to light is poor.
Parinaud’s syndrome - Etiology?
- Demyelinating disease
- Vascular disease affecting the dorsal midbrain
- Enlarged 3rd ventricle
Cranial nerve V - Applied anatomy - Sensory?
Facial sensation in 3 branches: V1, V2, V3.
CN V - Applied anatomy - Motor?
Muscles of mastication.
CN V - Exam - Inspection?
Inspect the patient’s face –> Wasting of the Temporalis will show as hollowing above the zygomatic arch.
CN V - Testing motor function?
- Ask patient to clench their teeth and feel both sides for the bulge of the Masseter and Temporalis.
- Ask the patient to open their mouth wide –> The jaw will deviate towards the side of the V lesion.
- Again ask them to open their mouth but provide resistance holding their jaw closed with one of your hands.
CN V - Testing sensory function?
- Assess light-touch for each branch and ask the patient to say ‘yes’ if they can feel it.
- For each branch, compare left to right. Ignore minor differences.
- Test pin-prick sensation at the same spots using a sterile pin.
- Temperature sensation is not routinely tested - Consider only if abnormalities in light touch and pin-prick are found.
- Use specimen tubes or other small containers full of hot or cold water.
CN V - Findings?
- Wasting of muscles
- Loss of ALL sensory modalities
- Loss of light touch only
- Loss of light-touch in V only
- Loss of pin-prick only
- Loss of sensation in a muzzle distribution (nose, lips, anterior cheek)
CN V - Wasting of muscles indicate?
- Long-term V palsy
- MND
- Myotonic dystrophy
CN V - Loss of ALL sensory modalities indicate?
V ganglion lesion (herpes zoster?)
CN V - Loss of light touch only?
With loss of sensation on ipsilateral side of the body –> contralateral parietal lobe (sensory cortex) lesion.
Loss of light touch in V only?
Lesion at sensory root pons.
Loss of pin-prick only?
Along with contralateral side of the body –> ipsilateral brainstem lesion.
Loss of sensation in a “muzzle” distribution (nose, lips, anterior cheeks)?
Damage to the lower part of the spinal sensory nucleus –> syringomyelia, demyelination.
CN V - Reflexes - Jaw jerk?
- Explain to the patient what is about to happen as this could appear rather threatening!
- Ask the patient to let their mouth hang loosely open.
- Place your finger horizontally across their chin and tap your finger with a patella hammer.
- Feel and watch jaw movement –> Should be a light closure but this varies widely in normal people.