CASE 6 - Multiple Sclerosis Flashcards
Epidemiology of MS for the following categories:
- Sex
- Age of onset
- Ethnicity
- Sex: females > males (3:1)
- Age of onset: 20-40 years
- Ethnicity: caucasian, mostly
MS prevalence is _______ in those who live FURTHER away from the equator
MS prevalence is greater in those who live FURTHER away from the equator
The presence of which allele is associated with greater MS risk?
HLA-DRB1
Which allele appears to be PROTECTIVE against MS?
HLA-A*02
List 4 environmental risk factors for MS
- Smoking
- Obesity in early life
- Low vitamin D levels
- Infection (EBV, HHV6)
List the 3 key pathophysiological mechanisms that are responsible for MS (DIA)
- Inflammation
- Demyelination
- Axonal degeneration
Explain the pathophysiology behind the most commonly-accepted theory of MS
MS is a Type IV Hypersensitivity reaction (cell-mediated)
- Activation of autoreactive T lymphocytes (which is activated by myelin)
- Inflammation: release of various cytokines that increase permeability of BBB
- These cytokines damage the oligodendrocytes AND allow more immune cells in
- Destruction of oligodendrocytes
- No myelin to cover neurons
- Leaves behind scar tissue / plaques / sclera
Inadequate remyelination means poor neuronal function
The focal demyelinated plaques of MS tend to occur in which CNS locations?
- Optic nerves
- Brainstem
- Spinal cord
- Cerebellum
- Juxtacortical and periventricular white matter
What is typically the earliest manifestation of MS?
Optic neuritis (caused by lesions in CN II)
Describe the clinical features of optic neuritis (earliest manifestation of MS)
- Typically unilateral
- Can be painful
- Decreased visual acuity
- Colour blindness
- Marcus Gunn pupil / relative afferent pupillary defect (RAPD)
Describe what is meant by a ‘Marcus Gunn pupil’
Marcus Gunn Pupil / Relative Afferent Pupillary Defect:
When a flashlight is swung between both eyes, the pupil with the RAPD will NOT constrict and may DILATE in response to light being shone in that eye.
The affected eye will still constrict as a consensual response (i.e. when the light is in the unaffected eye)
Internuclear ophthalmoplegia results from a lesion in which tract?
Medial longitudinal fasciculus
Describe what is seen in internuclear ophthalmoplegia
Impaired ADDUCTION of the AFFECTED eye, causing minimal adduction when trying to gaze contralaterally
(e.g. if the right eye is affected, trying to gaze to the left will cause the right eye to adduct minimally - it will stay in the middle. Meanwhile, the left eye adducts with no problem, but nystagmus is present)
- Intact convergence reflex
- More frequently bilateral than unilateral
https://en.wikipedia.org/wiki/Internuclear_ophthalmoplegia
What phenomenon is experienced by the patient who has internuclear ophthalmoplegia?
Diplopia
Describe the visual changes that can occur in MS (SIGNS)
- Optic neuritis
- Internuclear ophthalmoplegia
Describe the visual changes that can occur in MS (SYMPTOMS)
- Colour blindness
- Vision loss / blurred vision
- Central scotoma
- Pain
- Diplopia
List 5 clinical manifestations of Spinal Cord Demyelination in MS
- Lhermitte sign
- Pyramidal tract lesion (UMNL Sx)
- Involvement of dorsal spinal column (loss of vibration and fine-touch sensation, paresthesia, sensory ataxia)
- Neuropathic pain
- Absent abdominal reflex
What is Lhermitte sign?
A shooting electric sensation that travels down the spine upon flexion of the neck
Which clinical features can be present in someone with pyramidal tract lesions?
Upper motor neuron weakness:
- Spasticity
- Hyperreflexia
- Positive Babinski sign
Which clinical features can be present in someone with lesions of the dorsal spinal column?
The dorsal spinal column (proprioception, vibration, and fine touch) is the first sensory tract to be affected in MS.
- Sensory ataxia (e.g. positive Romberg’s)
- Paresthesias, numbness
- Loss of fine touch sensation
What is the Charcot neurological triad, and what are its clinical features? (SIN)
Charcot neurological triad: can occur in any cerebellar lesion.
- Scanning speech (slowed speech, recurrent pauses between syllables and emphasis on other syllables)
- Intention tremors
- Nystagmus
MS cranial nerve palsies can present with which clinical features?
- Diplopia
- Trigeminal neuralgia
- Facial palsy
Autonomic dysfunction as a result of MS can cause which clinical features?
- Bladder and bowel neurogenic disorders
- Impaired sexual function
Approximately __ to __% of patients with retrobulbar neuritis go on to develop MS
Approximately 20 to 50% of patients with retrobulbar neuritis go on to develop MS
Name the 3 patterns of MS
- Relapsing-remitting MS (RR-MS)
- Secondary progressive MS (SP-MS)
- Primary progressive MS (PP-MS)
Which pattern of MS is the most common?
Relapsing-remitting MS
Describe the 3 patterns of MS
- Relapsing-remitting MS (RR-MS): exacerbations occur, then symptoms improve and remain dormant for months-years.
- Secondary progressive MS (SP-MS): starts off similar to RR-MS with exacerbations followed by improvement, but the immune attack becomes more constant and disability progresses consistently.
- Primary progressive MS (PP-MS): one constant attack on myelin, causing consistent progression of disability
https: //www.youtube.com/watch?v=yzH8ul5PSZ8
What is the definition of an MS exacerbation?
New symptoms or significant worsening of existing symptoms, both of which last at least 24 hours and are preceded by at least 30 days of relative clinical stability.