CENTRAL NERVOUS SYSTEM Flashcards
CRANIAL NERVE DISORDERS - DEFINITION
- The cranial nerves are 12 pairs of nerves that emerge from the brain and are responsible for providing motor and sensory functions
- Cranial nerve disorder refers to impairment of one of the 12 cranial nerves that emerge from the underside of the brain, pass through openings in the skull, and lead to parts of the head, neck and trunk
CRANIAL NERVE DISORDERS - TYPES
- Trigeminal neuralgia
o Disorder of the 5th cranial nerve
o Sudden, severe, shock like symptoms across the face - Hemifacial spasm
o Where the blood vessels constrict the 7th cranial nerve
o Frequent involuntary twitching of the face - Glossopharyngeal neuralgia
o Compression of the 9th cranial nerve
o Sharp, jabbing px deep in the throat - Base skull tumours
o Can affect any nerve - Geniculate neuralgia
o Deep ear px - Occipital neuralgia
o Distinct type of headache
o Characterised by sudden and recurring jabs of piercing, throbbing, chronic px
CRANIAL NERVE DISORDERS - SIGNS AND SYMPTOMS
- Specific S&S depend on the cranial nerve that is affected
- Intermittent attacks of excruciating facial px
- Vertigo
- Hearing loss
- Weakness
- Paralysis
- Facial twitch
GLAUCOMA - DEFINITION
- Group of eye conditions that damage the optic nerve
- The optic nerve sends visual information from your eye to your brain and is vital for good vision
GLAUCOMA - CAUSE
- Glaucoma develops when the optic nerve becomes damaged
- As the nerve gradually deteriorates, blind spots develop in your vision
- This nerve damage is usually related to increased pressure in the eye
- Elevated eye pressure happens as a result of a build up of fluid that flows throughout the inside of the eye
- Fluid is known as aqueous humor
GLAUCOMA - CAUSE - OPEN-ANGLE GLAUCOMA
o Most common form
o Drainage angle formed by the iris and cornea remains open
o But other parts of the drainage system don’t drain properly
o This may lead to a slow, gradual increase in eye pressure
GLAUCOMA - CAUSE - ANGLE-CLOSURE GLAUCOMA
o Occurs when the iris bulges
o The bulging iris partially or completely blocks the drainage angle
o The fluid cant circulate through the eye and pressure increases
o May occur suddenly or gradually
GLAUCOMA - CAUSE - GLAUCOMA IN CHILDREN
o May be born with it
o Can also develop it within the first few years of life
o Blocked drainage, injury or an underlying medical condition may cause optic nerve damage
GLAUCOMA - CAUSE - PIGMENTARY GLAUCOMA
o Small pigment granules flake off from the iris and block or slow fluid drainage from the eye
o Leads to a deposit of pigment granules on tissue located at the angle where the iris and cornea meet
o Granule deposits cause an increase in pressure
GLAUCOMA - POPULATION AFFECTED
- People from black, Asian and Hispanic heritage over 40
- All other people over 60
GLAUCOMA - RISK FACTORS
- High internal eye pressure, also known as intraocular pressure
- Age over 55
- Black, Asian or Hispanic heritage
- Certain medical conditions
o Diabetes
o Migraines
o High blood pressure
o Sickle cell anaemia - Corneas that are thin at the centre
- Extreme near-sightedness or farsightedness
- Eye injury or certain types of eye surgery
- Taking corticosteroid medications, especially eye drops, for a long time
GLAUCOMA - CLINICAL PRESENTATION - OPEN ANGLE GLAUCOMA
o No symptoms in early stages
o Gradually, patchy blind spots in the peripheral vision
o In later stages, difficulty seeing things in your central vision
GLAUCOMA - CLINICAL PRESENTATION - ACUTE ANGLE-CLOSURE GLAUCOMA
o Severe headache
o Severe eye px
o Nausea or vomiting
o Blurred vision
o Halos or coloured rings around lights
o Eye redness
GLAUCOMA - CLINICAL PRESENTATION - NORMAL-TENSION GLAUCOMA
o No symptoms in early stages
o Gradually blurred vision
o In later stages, loss of side visio
GLAUCOMA - CLINICAL PRESENTATION - GLAUCOMA IN CHILDREN
o Dull or cloudy eye (infants)
o Increased blinking (infants)
o Tears without crying (infants)
o Blurred vision
o Near sightedness that gets worse
o Headache
GLAUCOMA - CLINICAL PRESENTATION - PIGMENTARY GLAUCOMA
o Halos around lights
o Blurred vision with exercise
o Gradual loss of peripheral vision
GLAUCOMA - PROGNOSIS
- There are treatments for glaucoma but no cures as it’s a lifelong condition
- Medications - Eye drops
- Laser therapy
- Surgery
o MIGS (minimally invasive glaucoma surgery)
o Can help slow down vision loss but cant restore lost vision or cure glaucoma - Glaucoma is a chronic and progressive condition that causes some degree of vision loss overtime
- Blindness is a rare complication so prognosis isn’t awful
PAPILLEDEMA - DEFINITION
- Medical term for swelling of the optic disc
- Almost always bilateral
PAPILLEDEMA - CAUSE
- High intracranial pressure causes papilledema
- Other causes include
o Hypertension
o Tumours
o Infection, bleeding or inflammation in the brain or the meninges
o Cerebral venous sinus thrombosis (blood clot in a vein in your brain)
o Iron-deficiency anaemia
o Medication use
o Idiopathic intracranial hypertension
PAPILLEDEMA - POPULATION AFFECTED
Overweight women
PAPILLEDEMA - RISK FACTORS
- Risk factors are those that raise intracranial pressure
o Space occupying lesions
Tumour
Subarachnoid haemorrhage
Decreased absorption of cerebrospinal fluid
Change in the dynamics of cerebrospinal flow through the ventricles
Increased production of cerebrospinal fluid (rare) - Risk factors for idiopathic intracranial hypertension include
o Recent weight gain
o Underlying associated conditions
Polycystic ovarian syndrome
Anaemia
Thyroid disease
Sleep apnoea
PAPILLEDEMA - CLINICAL PRESENTATION
- Some people have no symptoms
- Headaches
o May be worse in the mornings or when lying down - Transient visual obscuration’s
o Periods of about 5 to 15 seconds when vision gets blurry, goes grey or blacks out
o Usually happen when you change posture
o Can be unilateral or bilateral - Diplopia
- Nausea
- Vomiting
- Neurological symptoms
o May include problems with movement or thinking - Vision loss worsens as the condition progresses
PAPILLEDEMA - PROGNOSIS
- If its due to idiopathic intracranial hypertension you may be prescribed a carbonic anhydrase inhibitor such as acetazolamide
- If this doesn’t work surgical procedures are available
- Maintaining a healthy weight is a long-term strategy
- Should treat the underlying cause (if there is one)
- If it is caught early the outlook is good
- It needs to be treated because of the potential for blindness and other neurological effects
OPTIC NEURITIS - DEFINITION
Occurs when inflammation damages the optic nerve
OPTIC NEURITIS - CAUSE
- Exact cause is unknown
- Believed to develop when the immune system mistakenly targets the substance covering the optic nerve, resulting in inflammation and damage to the myelin
- The following autoimmune conditions are associated with optic neuritis
o Multiple sclerosis
o Neuromyelitis optica
o Myelin oligodendrocyte glycoprotein (MOG) antibody disorder
OPTIC NEURITIS - POPULATION AFFECTED
Females aged 20-40
OPTIC NEURITIS - RISK FACTORS
- Age - Adults 20 – 40
- Sex - Women much more likely
- Race - Occurs more often in white people
- Genetic mutations
OPTIC NEURITIS - CLINICAL PRESENTATION
- Usually only affects one eye
- Pain
o Often worsened by eye movement
o Sometimes the px feels like a dull ache behind the eye - Vision loss in one eye
o Most people have at least some temporary reduction in vision, but the extent of loss varies
o Noticeable vision loss usually develops over hours or days and improves over several weeks to months
o Vision loss is permanent in some people - Visual field loss
o Side vision loss can occur in any pattern, such as central vision loss or peripheral vision loss - Loss of colour vision
o Often affects colour perception
o Pt may notice colours appear less vivid than normal - Flashing lights
o Some people report flashing or flickering lights with eye movements
OPTIC NEURITIS - PROGNOSIS
- May resolve spontaneously without treatment
- If visual function is poor, a course of IV methylprednisolone (steroid medication) with a tapering course of oral steroids afterwards had been shown to speed recovery of visual function
- It improves in about 80% of pt over a few weeks
- Some people have continued visual change, reduced colour vision or more difficulty with night-time vision
- Occasionally it recurs and requires retreatment
- Many people have complete resolution of their symptoms
OPTIC NERVE ATROPHY - DEFINITION
- Optic atrophy is a condition that affects the cranial nerve
- The cranial nerve carries impulses from the eye to the brain
- Atrophy means to waste away or deteriorate
- It is not a disease in itself but is a sign of a potentially more serious condition
OPTIC NERVE ATROPHY - CAUSE
- Where something interferes with the optic nerves ability to transmit impulses
- The interference can be caused by numerous factors; including
o Glaucoma
o Stroke of the optic nerve
Anterior ischemic optic neuropathy
o A tumour that is pressing on the optic nerve
o Optic neuritis
An inflammation of the optic nerve caused by multiple sclerosis
o A hereditary condition in which the person experiences loss of vision first in one eye, and then in the other
Known as Leber’s hereditary optic neuropathy
o Improper formation of the optic nerve
Congenital problem
OPTIC NERVE ATROPHY - POPULATION AFFECTED
White people aged 10 – 50
OPTIC NERVE ATROPHY - RISK FACTORS
- High cholesterol
- High blood pressure
- Sudden drop in blood pressure or blood loss
- Swollen arteries in the head
- Clogged arteries
- Heart disease
- Diabetes
- Sleep apnoea
- Smoking
- Migraines
- Glaucoma
OPTIC NERVE ATROPHY - CLINICAL PRESENTATION
- Symptoms relate to a change in vision
- Specifically
o Blurred vision
o Difficulties with peripheral vision
o Difficulties with colour vision
o Reduction in sharpness of vision
OPTIC NERVE ATROPHY - PROGNOSIS
- No real cure or treatment
- Important to have regular eye exams
- Prognosis depends on what is causing the problem
o E.g. if the problem is optic neuritis, the pt can usually count on getting their vision back when the inflammation goes away
o If the cause is something else, the pt vision might not improve
OPTIC NERVE NEUROPATHY - DEFINITION
Sudden loss of vision due to an interruption of blood flow to the anterior of the optic nerve
OPTIC NERVE NEUROPATHY - TYPES
o Arteritic AION
Caused by inflammation of arteries supplying blood to the optic nerve
o Nonarteritic AION
Caused by reasons other than inflammation of the arteries
OPTIC NERVE NEUROPATHY - CAUSE - ARTERITIC AION
o Dangerous condition
o Caused by inflammation of arteries supplying blood to the optic nerve
o Inflammation is due to a condition called giant cell arteritis (GCA) or temporal arteritis, which caused inflammation of medium and large sized arteries
o 3x more common in women
o Most often affects people over the age of 55
OPTIC NERVE NEUROPATHY - CAUSE - NONARTERITIC AION
o Most common form of AION
o Majority of people affected are over 50
o Both men and women affected equally
o Caused by one of the following
A drop in blood pressure to such a degree that blood supply to the optic nerve is devreased
Increased pressure inside the eyeball
Narrowed arteries
Increased blood viscosity
Decreased blood flow to the optic nerve where it leaves the back of the eye
OPTIC NERVE NEUROPATHY - POPULATION AFFECTED
- Adults over 50
- A-AION – women more than men
OPTIC NERVE NEUROPATHY - RISK FACTORS
- High blood pressure
- Diabetes mellitus
- High cholesterol
- Smoking
- Sleep apnoea
- Heart disease
- Blocked arteries
- Anaemia or sudden blood loss
- Sudden drop in blood pressure
- Sickle cell trait
- Vasculitis
OPTIC NERVE NEUROPATHY - CLINICAL PRESENTATION - NA-AION
o Sudden, painless loss or blurring of vision in one eye
Usually noticed upon waking from a nights sleep or a nap
o Decreased visual activity
o Dyschromatopsia
o A RAPD
Relative afferent pupillary defect
o Swollen optic nerve with splinter haemorrhages
o Visual field defect
OPTIC NERVE NEUROPATHY - CLINICAL PRESENTATION - A-AION
o Px in the temples
o Px when chewing
o Scalp px or tingling
o Neck px
o Muscle aches and pains
Esp in upper legs or arms
o General fatigue
o Loss of appetite
o Unexplained loss of weight
o Fever
OPTIC NERVE NEUROPATHY - PROGNOSIS
- Prognosis depends on the type of optic neuropathy
- A-AION usually causes a greater degree of vision loss than NA-AION
- Degree of loss will depend on the location and amount of optic nerve that is damaged
- In NA-AION, about 40% of pt show some amount of improvement in central vision in the months after loss of vision or visual field
- Although 25% of pt with AION in 1 eye will develop it in the other eye in the next 3 years
- Treatment
o A-AION = basically the same treatment as giant cell arteritis (corticosteroid therapy)
o NA-AION = treatment is for the underlying cardiovascular disease or the risk factors that help trigger and aggravate NA-AION
MACULAR DEGENERATION - DEFINITION
- Also known as age-related macular degeneration
- An eye disease that affects central vision
- Top cause of vision loss in people over 50
- 2 types
o Dry (atrophic) - Up to 90% have the dry form
o Wet (exudative)
MACULAR DEGENERATION - CAUSE
- Inherited eye disease
- Occurs when the macula at the back of the eye starts to deteriorate for an unknown reason
MACULAR DEGENERATION - CAUSE - DRY
o Develops when tiny yellow protein deposits called drusen form under the macula
o The build-up deposits dry and thin the macula
o Vision loss tends to occur gradually
o Most people don’t completely lose central vision
MACULAR DEGENERATION - CAUSE - WET
o Occurs when abnormal blood vessels develop under the retina and macula
o The blood vessels leak blood and fluid
o Because of the fluid build-up a bulge forms in the macula
o May see dark spots in centre of vision
o Can quickly lead to total loss of central vision loss
MACULAR DEGENERATION - POPULATION AFFECTED
White people over 50
MACULAR DEGENERATION - RISK FACTORS
- Older age - Over 50
- Family hx
- Being overweight
- Smoking
- Hypertension
- Diet high in saturated fats
- Being of European descent
MACULAR DEGENERATION - CLINICAL PRESENTATION
- Many people don’t have symptoms until the disease progresses
- Blurred vision
- Blank or dark spots in field of vision
- The appearance of waves or curves in straight lines
MACULAR DEGENERATION - PROGNOSIS
- No cure
- Prognosis depends on degree of vision loss
- Not everyone will experience significant vision loss
- Many treatments
o Nutritional supplements
o Antivascular endothelial growth factor (anti-VEGF)
o Photodynamic therapy (PDT) - Many precautions you can take
o Quit smoking
o Lose weight
o Stay physically active
o Maintain healthy blood pressure and cholesterol levels
o Eat a healthy diet - Things that can help you live with it
o Wear eyeglasses or contact lenses
o Use brighter lights at home or at work
o Read with a magnifying device
HOW DIABETES AFFECTS THE OPTIC NERVE
- Diabetes can damage the eyes over time and cause vision loss, even blindness
- Eye diseases that can affect people with diabetes include
o Diabetic retinopathy
o Macular oedema
o Cataracts
o Glaucoma - Early diagnosis and treatment can go a long way toward protecting eyesight
- Managing diabetes and getting regular eye tests can prevent these conditions
HOW MULTIPLE SCLEROSIS AFFECTS THE OPTIC NERVE
- Visual problems is the first sign of MS in many people
- Eye diseases that can affect people with MS include
o Optic neuritis
o Nystagmus
o Diplopia - Prognosis is good for recovery from many vision problems associated with MS
HOW HYPERTENSION AFFECTS THE OPTIC NERVE
- High blood pressure can damage the tiny, delicate blood vessels that supply blood to the eyes
- This can cause
o Retinopathy
Damage to the blood vessels in the retina
o Choroidopathy
Fluid build-up under the retina
o Optic neuropathy
Nerve damage - Treatment and lifestyle changes can help control high blood pressure and reduce the risk of developing these eye diseases
HOW A B12 DEFICIENCY AFFECTS THE OPTIC NERVE
- Vitamin B12 plays an important role in the production of red blood cells
- It helps create and regulate DNA and aids in the function of brain cells
- Can cause
o Disturbed or blurred vision
o Optic neuropathy - Happens when the deficiency causes damage to the optic nerve that leads to your eyes
OCULAMOTOR NERVE PALSY - DEFINITION
- The oculomotor nerve is the 3rd of 12 cranial nerves (CN III)
- It is part of the autonomic nervous system
- It allows movement of the eye muscles, constriction of the pupil, focusing the eyes and the position of the upper eyelid
OCULAMOTOR NERVE PALSY - FUNCTION
- Controls 4 of the 6 muscles that enable eye movement
- Elevate the upper eyelid
- Focus the eyes
- Respond to light by making the pupil smaller
- Move your eyes inward, outward, up and down and control torsion
OCULAMOTOR NERVE PALSY - CAUSE
- Oculomotor palsy is a group of disorders affecting the CN III
- They occur when the third cranial nerve becomes paralyzed
- Can be present at birth
- May occur later in life due to
o Inadequate blood flow – causes a lack of oxygen that nerves need to function properly
o Nerve compression – abnormal pressure on a nerve - Conditions that may cause oculomotor palsy include
o Brain aneurysm
o Brain tumour
o Head injuries
o Demyelinating disease
Multiple sclerosis
o Microvascular disease
Diabetes
High blood pressure
o Infections
HIV
Lyme disease
o Migraine
TROCHLEAR NERVE PALSY - DEFINITION
TROCHLEAR NERVE PALSY - CAUSE
- When the trochlear nerve doesn’t function as it should, its often due to 4th nerve palsy – trochlear nerve palsy
- A palsy occurs when illness or injury paralyzes nerves that control muscle movements
- In some people its congenital
o They are born with it - It may also be due to trauma from rapid head movements
o Motor vehicle accidents - The trochlear nerve is one of the more fragile cranial nerves because its long and thin
- Sometimes occurs after minor injuries
- Less common causes include
o Cavernous sinus syndrome
When an abnormal growth affects the trochlear nerve
o Guillain-Barre syndrome
o Lyme disease
o Meningioma
o Microvascular coronary disease (MCD)
o Shingles (herpes zoster)
o Superior oblique myokymia
Episodes of involuntary superior oblique muscle tightening that distorts vision
TROCHLEAR NERVE PALSY - TREATMENT
- Treatment depends on what is causing symptoms
- Vision injuries causes by minor injuries often go away on their own
- For more severe palsy, treatments may include
o Eye patch to help the eye rest
o Special glasses to correct double vision
o Surgery to repair cranial nerve 4
TRIGEMINAL NEURALGIA - DEFINITION
- Causes painful sensations like an electric shock on side of face
- Chronic P affects trigeminal nerve, which carries sensations from face to brain
- Variety of treatment, effectively manage it- medications, injections or surgery