Neurology - Compressive and Demyelinating Illnesses of the CNS Flashcards
CNS damage from demyelinating disease
Damage to oligodendrocytes or their processes that myelinate axons
PNS damage from demyelinating disease
Damage to Schwann cells
1. genetic = impair ability to compact or produce myelin sheath
2. autoimmune
Immune mediated disease directed against CNS resulting in the loss of myelin and eventual loss of axons
Multiple Sclerosis
Most common demyelinating illness
Multiple Sclerosis
MS Epidemiology
3x more frequent in women; peak incidence 20-40 yo.
Candidate genes for MS
- HLA-II gene (responsible for antigen presentation)
- IL-2, IL-7, IL-17
Risk of first degree relative having MS
15x increase
Risk of identical twin having MS
150x increase
Possible non-genetic risk factors for MS
- Link to viral infection
- Reduced sun exposure and vitamin D
- Hx of other autoimmune disease
T/F: MS progresses straight to a chronic inflammatory picture with no preceding acute inflammation
True
Two phases of MS
1st - Active plaques: presence of typical leukocytes found during chronic inflammation
2nd - Inactive plaques: loss of axons, minimal inflammatory leukocytes, gliosis
T/F: Plaques are more prominent in areas rich in grey matter
False - they’re found in white matter rich areas
Helper T-cells initiate an immune response against what in MS?
Myelin basic protein - helps compact layers of myelin sheath
Major leukocytes involves in MS phase 1?
- Th cells (Th1 and Th17)
- B-cells
- Macrophages
- Cytotoxic T-cells
Areas that lymphocytes seem to reside “permanently” as MS flares continue? Where are they?
Lymphocytic follicles - prominent around meninges and blood vessels
MS plaques without prominent inflammation? With prominent inflammation?
Without = inactive (phase 2)
With = active (phase 1)
Axons tend to degenerate because…?
loss of myelin and oligodendrocytes => destabilization of action potentials => neuronal cell death
Most common initial Sx of MS (3)
- Paresthesia in 1+ extremities, trunk, or one side of face
- Weakness or clumsiness of a leg or hand
- Visual disturbances
Cognitive Sx of MS (3)
- Fatigue
- Depression
- Slowed cognition and memory effects
What is L’hermitte’s phenomenon?
Sensation of an electrical shock running down back and along the limbs
Motor Sx of MS (5)
- Bilateral, spastic weakness (lower extremities)
- Increased DTRs
- Charcot triad = dysarthria, nystagmus, tremor
- Facial twitching
- Slurred speech
Neurological Sx of MS (5)
- Dizziness
- Bladder dysfunciton
- Constipation
- ED in men/genital anesthesia in women
- Urinary/fecal incontinence (severe cases)
MS diagnosis criteria (3)
- Clinical diagnosis via MacDonald’s criteria
- Characteristic lesions on brain and spinal MRI
- Presence of certain types of Ab’s in the CSF
Most common progression of MS
Relapsing-remitting
(defn.) functional disturbance and/or pathological change in the PNS
Neuropathy
(defn.) pain in the distribution of a particular nerve, usually in the absence of objective signs
Neuralgia
(defn.) inflammation of a nerve
Neuritis
(defn.) pain along a dermatome, implying that the problem as at the level of the nerve root
Radiculopathy
(defn.) neuropathy of the entire plexus
Plexopathy
Polyneuropathy often presents as:
- Symmetrical distal weakness and sensory loss
- Hyporeflexia
What is multiple neuropathy?
Involves more than 1 nerve but not in a symmetrical fashion
What are some causes of multiple neuropathy?
Toxins, diabetes, AIDS, chronic inflammatory disease
Most common inherited neurologic disorder?
Charcot-Marie-Tooth Disease (a.k.a. Hereditary Motor and Sensory Neuropathy)
HMSN inheritance pattern?
Autosomal dominant inheritance - variable penetrance (not same severity in everyone)
Demyelination of peripheral nerves due to abnormal myelin production, damage to nerves, and thickened, palpable myelin sheaths
CMT1 pathophysiology
Axonal death and degeneration without a primary defect in myelin
CMT2 pathophysiology (less frequent)
CMTD Clinical Presentation (3)
- Slowly progressive distal symmetric muscle weakness and atrophy (champagne bottle legs)
- Proprioception and touch mainly affected
- Nerves can become enlarged and palpable
Most common cause of acute flaccid paralysis?
Guillain-Barre Syndrome (GBS)
When does GBS typically occur?
Following an infection (with flu-like sx) - infection may be CMV, EBV, mycoplasma pneumoniae, or prior vaccination
Cells that aid in destruction in GBS?
- T-cells = recognize and cause segmental demyelination
- Macrophages
- Antibodies
In GBS, when myelin is destroyed, destruction is accompanied by ________.
Inflammation
Are axons (often) left intact in GBS?
Yes, even though Schwann cells are destroyed
What happens after 2-3 weeks of demyelination with GBS?
Schwann cells begin to proliferate => inflammation subsides => re-myelination begins
Clinical features of GBS (3)
- Acute, rapid, progressive inflammatory polyradiculopathy
- predominantly MOTOR Sx
- Ascending Sx (Legs up)
Severe GBS can progress to loss of what funciton?
Function of the cervical spinal cord
Treatment of GBS (3)
- Protect airway/ventilation
- Plasmapheresis
- IV immunoglobulins
What can/does compression of a nerve in the PNS lead to?
- Pain
- Reduction or loss of function (motor (sometimes also autonomic) and sensory)
Direct mechanical damage to the nerve leads to…?
Loss of axonal function (crush injury)
Compression of the vessels in the perineurium (ischemia) leads to…?
decreased blood flow and reduced function in the nerve
What is impingement of a nerve?
Inability to “glide” along its course => explains Sx dependant on position
Most common cause of unilateral facial paralysis?
Bell’s Palsy
Bell’s Palsy is thought to be compression of the facial nerve from inflammation/edema caused by what?
Herpes virus
Compression of CN7 in occurs in what narrow compartment of the temporal bone?
Petrous portion
Clinical Features of Bell’s Palsy (6)
- Acute onset (48 hr) of unilateral facial paralysis
- Posterior auricular pain, earache
- Decreased tearing
- Hyperacusis (reduced sound tolerance)
- Taste disturbances
- Poor eyelid closure on affected side
