Chapter 26- Peripheral Nerves And Muscles Flashcards
What are the portions of myelinated nerves separated by
Internodes called Nodes of Ranvier
What supplies the myelin sheat for each internode
Single schwann cell
What is the epineurium
Enclosed entire nerve
What is the perineurium
Multilayered, concentric connective tissue sheath that encloses each fascicle
What is the endometrium
Surrounds the individual nerve fiber
What is the result when there is Schwann cell demyelination
Segmental demyelination, with loss of myelin
What is the result when there is axonal degeneration
Primary involvement of the neuron and its axon
*May be followed by axonal regeneration and reinnervation of muscle
What is a denuded axon
Stimulus in the axon for remyelination
What is the length of neurons that have been remelinated following injury
Shorter than normal
What is the first thought when there is the appearance of onion bulbing of a neuron
There is degeneration of axon as it is losing and unraveling of the myelin
What is a traumatic neuroma
There is a trauma to the nerve, and rather than the repairing in the parallel normal fiber pattern, there is haphazard whirled proliferation that is prone to painful nodules
What are myelin ovoids
Schwann cell’s catabolize myelin and then later engulf the axon fragments, which produce small oval compartments
What is the result when muscles lose innervation due to axonal degeneration
Denervation atrophy
What are angulated fibers
Atrophic fibers are smaller and triangular shape when denervation atrophy
What are target fibers when there is axonal degeneration
Rounded zone of disorganized myofibers in center of the muscle fiber
What determines the muscle fiber type
The motor neuron, as all muscle fibers of a single unit are of the same type
What is steroid atrophy
During glucocorticoid therapy, type 2 muscles can atrophy
What is segmental necrosis
Destruction of a portion of myocyte, followed by myophagocytosis, which leads to the deposition of collagen and fat
During regeneration of muscle fibers, what changes are seen with regards to the nuclei
Regenerating portion has a large, internalized (central location) nuclei with Prominent nucleoli, and cytoplasm that is laden with RNA that is Red
What is mononeuritis pultiplex and what is a common cause
Several nerves damaged in a haphazard fashion
*Usually cause by vasculitis, such as polyarteritis nodosum.
What is the cranial nerve that can cause facial muscle paralysis
Cranial nerve 7
What is Bell’s palsy
One sided facial drooping
What is associated with causing Bell’s palsy
- Upper respiratory infection
- Diabetes mellitus
What are the common causes for neurogenic bladder
Aka lack of control of urinary conditions due to an underlying issue
1) Nerve damage (seen in MS or parkinson, or DM)
2) Infection/injury of brain or SC
3) Heavy metal poisoning
4) Spina bifida and other congenital SC issues
What are the state of the reflexes and order or paralysis in Guillain-Barre
Deep tendon reflexes disappear
*Ascending paralysis
What are the common caused of GBS
*2/3 proceeded by acute influenza like illness
- CMV
- EBV
- Mycoplasma
- prior vaccination
What portion of the neuron tends to be affected by GBS
- Perivenular and endometrial infiltration with inflammatory cells
- segmental demyelination
Are antibodies present in GBS
Yes, they are antimyelin Abs
What are the cytoplasmic processes involved in GBS
Macrophages penetrate basement membrane of Schwann cells, particularly near the Nodes of Ranvier
What are the lab CSF values in the cause of GBS
- Increased protein (due to permeability of spinal roots)
- Normal inflammatory cells (they are confined to the roots)
What are the common causes of death in GBS and what is the treatment
Respiratory paralysis
Autonomic instability
Cardiac arrest
*Treatment is plasmaphareisis or IVIg
How is chronic inflammatory demyelination get polyradiculneuropathy differentiated from GBS
- It will respond to steroids
- symptoms will be present for >2 months
What is the classic histological finding in the case of chronic inflammatory demyelinating polyradiculoneuropathy
Onion bulbs
What are the characteristics at the neuron level in leprosy
- Segmental demyelination
- remyelination
- Loss of both myelination and unmyelinated axons
-Endoneuronal fibrosis and multilayered thickening of perineural sheaths
Which neurons tend to be affected in leprosy
Cool extremities (lower temps for the Mycobacterium to growth)
Which fibers tend to be affected in leprosy
Pain fibers, with the loss of sensation contributing to injury
What are the neurons that tend to be affected during infection with diptheria
Selective demyelination of axons that extend into the anterior and posterior roots, along with mixed sensorimotor nerves q
How does VZV cause damage to neurons
Infects the neuron, then causes the loss of the affected ganglion, leading to regional necrosis and hemmorhage
**Loss of the dorsal root sensory ganglion results in axonal degeneration of peripheral nerves
What kind of neuron damage is occuring in DM
Segmental demyelination with loss of small myelinated and unmyelinated fibers
*Also loss of autonomic fibers
Which thyroid dysfunction can result in neuropathy
Hypothyroidism
Which paraneoplastic syndromes can cause neuropathy
Small cell lung cancer
Which neoplasms can cause neuropathy
B cell neoplasms (monoclonal gammopathies)
What are the syndromes that B cell neoplasms can cause
- Polyneuropathy
- Orangomegaly
- Endocrinopathy
- Monoclonal gammopathy
- skin changes
Which nerve is affected in saturday night palsy
Radial nerve upper arm
WHich nerve can be affected at the knee
Fibular nerve
What is Morton neuroma
- Metatarsalgia
- Interdigital nerve @ intermetatarsal sites
*Perineural fibrosis is histological findings
What is the most common inhereted peripheral neuropathy
Charcot-Marie-Tooth (CMT)
What is the inheritance pattern and gene in CMT1
Autosomal dominant
-Chromosome 17, peripheral myelin protein (PMP22)
*Seen in the second decade of life
What is the inheritance form of CMTX
X linked
What is the inheritance pattern and gene present in CMT2
Autosomal dominant
Due to axonal injury
- MDN2 gene, normal mitochondrial fusion
- Seen in early childhood
What is the mechanism of disease in the case of myasthenia gravis
There are antibodies that target the acetylcholine receptors
What is the mechanism of disease in Lambert-Eaton
Antibodies block ACh release by inhibiting the presynaptic calcium channel
In those patients with myasthenia gravis who do not have Abs to AChR, what are they to
Sarcolemmal protein muscle specific receptor tyrosine kinase
What is the most common causes for Lambert-Eaton Myasthenic syndrome
Paraneoplastic conditions, with about 50 being from a small cell lung cancer
What is the staining in the cause of myocytes undergoing regenerations
Basophilic staining, aka RED due to the height number of RNA
When does dermatomyositis commonly occur
4th-6th decade
What conditions has a distinctive lilac or helipotrope discoloration of upper eyelids and periprbital edema
Dermatomyositis
Which lesions are commonly seen with dermatomyositis
- Lilac with eyelids
- telangiectasias of nail folds, eyelids, and gums
- Groton lesions
What are Groton lesions that are associated with dermatomyositis
Scaling erythematous eruptions or dusky patches over the knuckles, elbows, or knees
Which muscles tend to be affected first with dermatomyositis
Proximal muscles (raising chair or climbing stairs)
What conditions are those with dermatomyositis at an increased risk for
- dysphagia (oropharyngeal and esophageal muscles)
- Interstitial lung disease
- Cardiac involvement
**Increased visceral cancer risk
What are the autoantibodies that are commonly present in dermatomyositis
Anti-Mi2
Anti-Jo1
AntiP155/P140
In those with dermatomyositis, which symptoms are expected in the presence of autoantibodies to:
-Anti-Mi2
Heliotrope rash and Groton papules
In those with dermatomyositis, which symptoms are expected in the presence of autoantibodies to:
-anti-Jo1
Mechanic hands
In those with dermatomyositis, which symptoms are expected in the presence of autoantibodies to:
-antiP155/P140
Paraneoplastic and juvenile cases
What is the common histological findings in dermatomyositis
Perifascicular atrophy
*Atrophic fibers grouped at the periphery of fascicles
In juvenile dermatomyositis, which organs are commonly affected
- most common myopathy of children
- Involves the GI (mucosal ulcers, perforation)
During polymyositis, which muscles are affected first
Symmetrical proximal muscle involvement
What is the clinical features seen in a patient with polymyositis
Myalgia and weakness
Adult onset
No Cutaneous features
*Diagnosis of exclusion
What are the histological findings in polymyositis
CD7 T cells in the endometrium, necrotic and regenerating fiber scattered through the fascicle
- endomysial mononuclear infiltrate (differentiated that dermatomyositis)
- *Random distribution of affected fibers
What is the clinical features of inclusion body myositis
Slowly progression of muscle weakness, especially in the quadriceps and distal UE
*Starts with the distal muscle and extensors of knees and flexors of wrists and fingers (asymmetric)
Rimmed vacuoles are seen in which condition
Aka inclusions with reddish granular rimming
Highlighted by Basophilic granules around the periphery, endpmysial fibrosis seen in inclusion body myositis
What is the treatment for inflammatory myopathies
Usually responds poorly to steroids
Chloroquine and hydroxychloriquine commonly affect which part of the body
*Used in the treatment of malaria
Causes lysosomal storage myopathy, leading to slowly progressing muscle weakness due to type 1 fiber disruptions
Alcohol binge drinking can have what effect on muscles
Rhabdomyolysis
What is the gene affected in DMD
Xp21, which codes of dystrophin
What is the level of dystrophin in the case of DMD
Absent
What is the level of dystrophin in the case of BMD
Decreased amount of DMD
Which complication tends to arise in those with DMD or BMD
Cardiac manifestations
What i sthe state of muscle size in those patients with DMD
Enlarged due to increased bulk that turns to fat and connective tissue
What is myotonia seen during myotonic dystrophy
Sustained contraction of a group of muscle
*Can be elicited by percussion on the thenar eminence
What is the genetic component seen during myotonic dystrophy
CTG trinucleaotide repeats leading to DMPK
What are the symptoms in a patient with myotonic dystrophy
- Stiffness, difficulty releasing grip
- Skeletal muscle weakness
- cataracts
- Endocrinopathy
- Cardiomyopathy
Which condition can be described with:
- Ring fiber
- Sarciplasmic mass
- Hatchet face
Myotonic dystrophy
Patients with emery dreifuss muscular dystrophy (EMD) have mutation in which gene
EMD1 (x linked)
EMD2 (AD)
*Both code for nuclear lamina proteins
What is the triad seen in those patients with emery dreifuss musclar dystrophy (EMD)
1) Slowly progressing hymeroperoneal weakness
2) Cardiomyopathy with conduction defects
3) Early contractures of the Achilles’ tendon, spine, and elbows
What is the most common disease of lipid or gylcogen metabolism
Carnitin palmitolytransferase 2
What are the symptoms seen in those with carnitine palmitolytransferase 2
Episodic muscle damage with exercise and fasting
What are the lab values that will be seen in those with mitochondrial myopathies
Weakness, increased serum creatinine kinase, rhabdomyolysis
What are the muscle commonly seen to be affected in those with mitochondrial myopathies
Extraocular muscle involvment
*Chronic regressive external ophthalmologist common
What is the mutation in Levers
Point mutation in mitochondrial DNA leading to hereditary optic neuropathy
What is the conditions being caused by Leigh syndrome
Subacute necrotizing encephalopathy
What is the condition being caused during Barth syndrome
Infantile x linked cardio skeletal myopathy
What is the condition being caused during Kearns-Sayre syndrome
Weakness of the extraocular muscles
Deletions or duplication of the mitochondrial DNA
*Also will ahve ophthalmoplegia, pigmentary degeneration of retina, complete heart block
What does red, trichromatic stains showing “ragged” fibers mean
Aka aggreagated of abnormal mitochondria under the sarcolemma with distortion of myofibrils
**aka parking Lot inclusions
What is the congenital cause of floppy infant due to
Spinal muscular atrophy
What are some of the symptoms seen in spinal muscular atrophy
Congenital: -Myotonia -Myopathy -muscular dystrophies Encephalopathy
Muscular trophy destroys what component
Anterior horn cell of the SC
What is the gene factor affected in spinal muscular atrophy
Survival motor neuron 1 (SMN1)
What is the most common form of spinal muscular atrophy
Wernig Hoffman (SMA type 1)
- onset at birth, floppy baby and death <3 yo
- Truncal weakness and loss of chewing swallowing, and breathing
Which gene and product is the result of malignant hyperthermia
RYR1 mutation, leading to events in the calcium channel
