Exam 2: PNS Flashcards
Myasthenia
Painless weakness
Pathology of any portion of motor unit may cause
Skeletal muscle dysfunction
Axon neuropathy involved direct injury to
Axon
Areas of injury for PNS damage
Lower motor neuron/ peripheral axon
NMJ
Innervated myoctyes
Myelin in PNS created by
Schwann cells
2 types of neuropathy
Axonal
Demyelinating
Wallerian degeneration
Distal to injury breaks down
Demyelinating neuropathy involves damage to
Myelin or Schwann cells
Peripheral neurons have ability to
Regrow
Remyelinate
With regrowth and demyelination of PNS…
Low axon density
Low amplitude on NCV
Demyelinating neuropathy spares
Axon
Segmental demyelination
Random demyelination
Repair of demyelinating neuropathy
Thin myelin
Short internodes
Mononeuropathy always involves either
Entrapment
Trauma
Polyneuropathy involves
Many nerves damaged from metabolic problems
Stocking and glove paresthesia observed in
Polyneuropathy
Rubbery legs, ascending paralysis, and respiratory failure observed in
GBS
Guillain-Barre Syndrome (GBS)
Acute motor neurons demyelination
Autoimmune
Age and sex MC in GBS
Males
15-35 or 50-60
Causes of PNS injury
Malnutrished Toxic Vascular Inflammatory Genetic
Most cases of GBS ___
Self-resolve
___ near motor nerve roots in GBS
Macrophages
Treatment for GBS
Ventilation
IV ABs
Chronic inflammatory demyelinating polyneuropathy (CIDP)
Chronic version of GBS
Sensorimotor abnormalities at least 2 months
Schwann cells resembling onion bulbs observed in
CIDP
Age and sex MC for CIDP
Males 2X
40-60 yo
Microangiopathy drives
Diabetes problems
In diabetes, ROS damages
Vasa nervorum
Nerve injury in diabetes begins with
Decrease sensation
Treatment for diabetic peripheral neuropathy
Glucose control
Daily inspection
Analgesics
Anticonvulsants
Diabetic peripheral neuropathy injures both
Myelin and axons
Microangiopathy in diabetes peripheral neuropathy damages PNS neurons especially in the
Retina
Kidney
Neuropathic arthropathy involves progressive degeneration of
Weight bearing joints
Foot, ankle, hip
TM and MP joints
Neuropathic arthropathy can be a complication of any neuropathy, particularly
DM
Spinal cord injury
Syphilis
Leprosy
Neuropathic arthropathy causes decrease sensation, cause
Unperceived trauma
Environmental exposure that damages peripheral nerves affects
Longest neurons
Mononeuritis multiplex
Neuronal damage from vasculitis
Charcot-Marie-Tooth disease
Inherited conditions of axonal or demyelinating neuropathy
CMT disease due to
PMP22 mutation
Variable severity is observed in CMT disease, common symptoms are
Pes cavus
Altered gait
Myasthenia gravis
Autoimmune attack on post-synaptic ACH receptors
Extraocular weakness, including ptosis and diplopia, seen in
Myasthenia gravis
60% cases myasthenia gravis due to ____ and 20% due to ____
Thymus hyperplasia
Thymoma
Age and sex for myasthenia gravis
Females MC : 20-30
Males: 50-70
Tensilon test inhibits ___ and is used in ___
Antibodies
Myasthenia gravis
Lambert-Eaton Syndrome (LES)
Autoantibodies against pre-synaptic Ca2+ channels
Symptoms worsening throughout the day is characteristic of
Myasthenia gravis
LES inhibits ___, causing girdle weakness
ACH release
LES improves with
E-stimulation
Elderly autoimmune attack
LES
Paraneoplastic syndrome can cause
LES
Tetanus
Clostridium tetani increases ACH release
Spasm
Botulism
Clostridium botulinum inhibits ACH release
Descending paralysis
Floppy infant syndrome due to botulism can be due to
Soil or honey
Infant botulism effects ages
6 weeks - 6 mo
Myopathy
Primary disease of muscle
Type 1 myofiber type
Slow twitch
Aerobic
Fat
Type 2 myofiber type
Fast twitch
Anaerobic
Glycogen
Disuse atrophy affects
Type 2
Glucocorticoid atrophy affects
Type 2
Cushing syndrome
Elevated cortisol
Myasthenia
Painless muscle weakness
Neuropathic changes cause
Grouped atrophy
Cushing syndrome can be due to
External corticosteroids (MC)
Adenoma (pituitary or adrenal)
Features of Cushing syndrome
Weight gain Moon facies Purple striae Buffalo hump Insomnia Infertility Hirsutism
Cushing syndrome MC in
Young adult females
Inherited skeletal muscle disorders include
Muscular dystrophy
2 types of muscle dystrophy
- Duchesse muscular dystrophy
2. Becker muscular dystrophy
Inheritance of dystrophinopathies
X- linked (xp21)
In muscular dystrophy, ____ outpaces repair due to mutated dystrophin
Myocyte degeneration
Duchenne MD
Absent dystrophin
1 in 3500 males
Childhood weakness
Fatal
Becker MD
Abnormal dystrophin (variable)
1 in 30000 males
May have normal life
___ always lethal
Duchenne MD
Features of dystrophinopathies
Clumsiness Weakness Fatigue Pelvic girdle weakness -> gower sign Pseudohypertrophy of calves Cardiorespiratory insufficiency
In labs, high ___ observed in dystrophinopathies
Creatine kinase
Gower sign MC associated with
Duchenne MD
Graves’ disease
Autoimmunity against TSH receptor
Graves’ disease MC in
Females
Graves’ disease causes hyperthyroidism, resulting in
Elevated T3 and T4
Signs of Graves’ disease
Goiter Exophthalmos Pretibial myxedema Insomnia Weight loss Fatigue Irregular HB
Pseudohypertrophy of calf muscles in DMD due to
Fibrofatty inflitrate
Muscular dystrophies are lethal due to
Cardiorespiratory insufficiency
Thyrotoxic myopathy
Overproduction of thyroxine
Ethanol myopathy
Binge drinking
Graves can cause
Thyrotoxine myopathy
MC drug myopathy
Statins myopathy
Drug myopathy is usually w/o
Inflammation
Types of toxic myopathies
Thyrotoxic
Ethanol
Drug
Ethanol myopathy can progress to
Acute renal failure
Schwannoma
Benign peripheral nerve sheath tumor
Most schwannomas are
Sporadic and involve CN 8
Schwannomatosis
Multiple CNS and cutaneous schwannomas
Schwannoma aka
Acoustic neuroma
Schwannoma can cause
Tinnitus
Vertigo
Headache
Hearing loss
Neurofibromas
Benign nerve sheath tumors
Neurofibromatosis type 1 (NF1)
Pronounced neurofibromas
Vascular stenosis
NF1 due to
Mutation in chromosome 17 (autosomal dominant)
Freq of NF1
1 in 3,000
NF1 can have 3 distinct characteristics
Lisch nodules
Axillary freckling
Cafe au lait spots
NF2 due to
Mutated Merlin gene
NF2 results in
Bilateral vestibular schwannomas
NF2 results in risk for CNS tumors, including
Ependymomas
Meningiomas
Freq of NF2
1 in 50,000
Malignant peripheral Nerve sheath tumor (MPNST)
Malignant Schwann tumor mixed with neuronal connective tissue
MPNST associated with
NF1
MPNST is large in infiltrative, affecting
Arms
Legs
MPNST is
Painless and edematous
Traumatic neuroma
Non-neoplastic growth of nerve tissue, following trauma to nerve
Traumatic neuroma MC due to
Surgery
NF2 has no
Cutaneous lesions
Traumatic neuroma is painful and
Non-invasive
