Neuromuscular I (Neurophys, Plexopathy, Neuropathy) Flashcards
AR disorder with childhood-onset sensorimotor neuropathy, corticospinal degeneration, and optic neuropathy, with walking in inside of feet and tightly curled hair.
Gene?
Pathological finding?
Giant axonal neuropathy (GAN)
GAN gene - gigaxonin (cross linking of intermediate filaments)
Pathology: Large focal axonal swelling (which contains disorganized neurofilaments)
AD disorder with sensorimotor neuropathy, ataxia, hearing loss, and anosmia, as well as retinosis pigmentosa, cardiomyopathy, and skin changes.
What is elevated?
Treatment?
Refsum’s disease
Accumulation of phytanic acid.
Treatment includes dietary restriction of phytanic acid
AR disorder with neuropathy and retinosis pigmentosa, associated with intestinal pseudo-obstruction.
Myoneurogastrointestinal encephalopathy (MNGIE)
AR disorder with neuropathy, ataxia, and retinosis pigmentosa, associated with acanthocytes on smear.
Genetic mutation?
Lab finding?
Treatment?
Abetalipoproteinemia
Mutation in microsomal triglyceride transfer protein (MTTP)
Lab: Low vitamin E and beta-lipoprotein
Treatment: Vitamin E supplementation and fat restriction (especially long-chain saturated fatty acids), especially
What does the F wave reflect?
How is it obtained?
Measurement of muscle response after antidromic signal to motor neuron and then bounce-back of orthodromic signal down to the muscle
Supramaximal stimulation of a motor nerve
What does the H wave reflect?
How is it obtained?
S1 reflex arc, equivalent to ankle reflex (signal travels up tibial nerve through sensory afferent, signal in cord goes to motor neuron and stimulates muscle to contract)
`
Stimulate tibial nerve at popliteal fossa and record at soleus.
Types of muscle fibers. Which are fast? Which are oxidative vs glycolytic?
Type I: Slow oxidative
Type IIa: Fast oxidative
Type IIb: Fast glycolytic (anaerobic)
Motor branches of median nerve that branch after the carpal tunnel?
Thenar/recurrent motor branch to thenar muscles (leads to weakness in thumb abduction and opposition)
Brachial plexus:
Which nerves branch directly off roots, and which roots?
What muscles do they supply?
Dorsal scapular (C5): Rhomboids and levator scapulae
Long thoracic (C5-C7): Serratus anterior
Brachial plexus:
Which nerves branch directly off trunks, and which trunk?
Which muscles do they supply?
Subscapular nerve (Upper trunk) - Supraspinatus and infraspinatus
Nerve to subclavius (Upper trunk)
No nerves directly off middle or lower trunk
Brachial plexus:
Inputs to each of the cords
Lateral: Anterior divisions of upper and middle trunks (C5-C7)
Medial: Anterior division of lower trunk (C8-T1)
POsterior: posterior divisions of all 3 trunks (C5-T1)
Brachial plexus: nerves coming off lateral cord before terminal branch?
Terminal branch?
Before terminal:
1. Lateral pectoral nerve (pectoralis major)
Terminal branches:
1. Median nerve (also contribution from medial cord)
2. Musculocutaneous nerve
Brachial plexus: nerves coming off posterior cord before terminal branch?
Terminal branch?
Before terminal:
1. Upper subscapular nerve (subscapularis)
2. Lower subscapular nerve (teres major and lower part of subscapularis)
3. Thoracodorsal nerve (latissimus dorsi)
Terminal branches:
1. Axillary nerve
2. Radial nerve
Brachial plexus:
Nerves coming off lateral cord before terminal branch?
After terminal branch?
Before terminal:
1. Medial pectoral nerve (pectoralis minor)
2. Medial brachial cutaneous nerve (sensory to medial arm)
3. Medial antebrachial cutaneous nerve (sensory to medial forearm)
Terminal
1. Ulnar nerve
2. Gives branches to median nerve
Mutation associated with familial amyloid polyneuropathy types 1 and 2?
Transthyretin
(Type 1 is more severe and has more autonomic involvement, type 1 is milder and has less autonomic involvement, carpal tunnel can be prominent feature)
Which CMTs are demyelinating?
CMT1 and CMTX
CMT4 is both demyelinatig and axonal
CMT inheritence by type
CMT1: AD
CMT2: AD except one subtype of CMT2A
CMT3: can be AD or AR - not a very useful term since caused by same genes as CMT1A (AD), CMT1B (AD), CMT1D (AD), or CMT4 (AR) - distinguished by severe, childhood onset
CMT4: AR
CMTX: X-linked
Median nerve muscles innervated by:
- Muscular branches from cubital fossa
- Anterior interosseous nerve
- After passing through carpal tunnel
Muscular branches from cubital fossa are forearm muscles
1. Pronator teres
2. Flexor carpi radialis
3. Flexor digitorum superficialis
4. Palmaris longus
Anterior interosseous nerve:
1. Flexor digitorum profundus
2. Flexor pollicis longus
3. Pronator quadratus
After carpal tunnel:
Muscular branch to thenar muscles:
1. Abductor pollicis brevis
2. Flexor pollicis brevis (superficial part, deep is ulnar)
3. Opponens pollicis
Digital branch:
1. 1st and 2nd lumbricals (Flex MCP amd extend PIP and DIP)
Tensor fascia latae:
- Role
- Innervation
- Roots
Role: hip aBduction when hip is flexed
Nerve: Superior gluteal nerve
Root: L4-S1
Lumbar plexus:
- Nerve roots
- Major nerves (3)
- Minor nerves (3)
Roots: T12-L4
Major nerves:
1. Femoral
2. Obturator
3. Lateral femoral cutaneous
Minor nerves:
1. Iliohypogastric
2. Ilioinguinal
3. Genitofemoral
What is the lumbosacral trunk?
Fibers from L4 and L5 that join the sacral plexus to form the sciatic nerve.
Lateral femoral cutaneous nerve: roots
L2, L3
Femoral nerve roots
L2, L3, L4 (posterior divisions - obturator is anterior divisions)
Obturator nerve roots
L2, L3, L4 (anterior divisions - femoral is posterior divisions)
Muscles innervated by obturator nerve, anterior and posterior divisions
Anterior division:
1. Adductor brevis
2. Adductor longus
3. Gracilis (another adductor)
Posterior division:
1. Obturator externus (external hip rotation)
2. Adductor magnus (also innervated by sciatic nerve)
Muscles innervated by femoral nerve
- Iliacus (also direct banches form lumbar plexus; hip flexion)
- Pectineus muscle (hip flexion and adduction)
- Sartorius muscle (thigh abduction, flexion, and external roation)
- Quadriceps muscles: Vastus lateralis, vastus intermedius, vastus medialis, and rectus femoris
Sensory branches of femoral nerve
Anterior femoral cutaneous (L2-3)
Saphenous nerve (L3-4, medial calf)
Sacral plexus:
- Nerve roots
- Nerves (6)
Roots: L4-S4 (L4 and L5 via lumbosacral trunk to sciatic and gluteal nerves)
Nerves:
1. Tibial (sciatic)
2. Peroneal (sciatic)
3. Superior gluteal
4. Inferior gluteal
5. Posterior cutaneous nerve of the thigh
6. Pudenal nerve
Superior gluteal nerve
- Nerve roots
- Muscles innervated
- Movements
Roots: L4-S1
Muscles:
1. Gluteus medius
2. Gluteus minimus
3. Tensor fasciae latae
Motements:
Hip aBduction: glut medius and minimus when hip extended, TFL when hip flexed)
Nerves supplying hip aDduction and hip aBduction
ADduction:
1. Obturator (L2-L4, Adductor brevis, adductor longus, gracilis)
2. Tibial portion of sciatic nerve (Adductor magnus)
ABduction: Superior gluteal nerve (L4-S1, gluteus medius, gluteus minimus, TFL)
Inferior gluteal nerve
- Nerve roots
- Muscles innervated
- Movements
Roots: L5-S2
Muscles: Gluteus maximus
Movements: thigh extension
Posterior cutaneous nerve
- Nerve roots
- Area supplied
Roots: S1-S3
Supplies lower buttock and posterior thigh
Pudendal nerve
- Nerve roots
- Area supplied
Roots: S2-S4
Supplies peineal and perianal sensation
(Also motor to pelvic muscles)
Gene affected in HNPP (hereditary neuropathy with liability to pressure palsies)
Inheritence?
PMP22 deletions (periperal myelin protein 22) (note duplications in the same gene cause CMT 1A)
Autosomal dominant with incomplete penetrance
Tibial nerve muscles supplied in thigh (via sciatic) and lower leg
Thigh
1. ADductor magnus (hip aDduction, also some supply from obturator)
Hamstrings which all flex knee and extend hip:
2. Semimebranosus
3. Semitendinosus
4. Long head of biceps femors (short head is by common peroneal)
Lower leg
1. Gastrocnemeius (calf, ankle plantarflexion and knee flexion)
2. Soleus (calf, plantaflexion)
3. Tibialis posterior (deep to calf, plantarflexion and ankle inversion)
Peroneal nerve muscles supplied in thigh (via sciatic) and lower leg (superficial and deep peroneal)
Thigh:
1. Short head of biceps femoris
Superficial peroneal: foot eversion
1. Peroneus longus
2. Peroneus brevis
Deep peroneal:
1. Tibialis anterior (dorsiflexion)
2. Extensor hallicus (first toe extension)
3. Extensor digitorum longus and brevis (toe extension)
4. Peroneus tertious (eversion and dorsiflexion)
Foot drop: effects of inversion and eversion with L5, common peroneal, and deep peroneal
L5: both inversion (tibialis posterior, tibial nerve) and eversion (common->deep peroneal affected)
Common petoneal: inversion spared, eversion affected
Deep peroneal: both inversion and eversion spared (eversion is mostly superficial peroneal)
Weakness patter in femoral nerve lesions in retroperoteneal/intrapelvic space vs inguinal ligament
Retroperoteneal/intrapelvic space: hip flexion involved (liacu off proximal femoral nerve, and also potentially psoas which is directly of lumbar plexus right before femoral nerve leaves)
Inguinal ligament: hip flexion spared
(Psoas and iliacus branch off proximal to the inguinal ligament)
Psoas muscle innervation
Direct branches of lumbar plexus (L1-L3, anterior divisions)
Distal symmetric primary pain/temperature neuropathy with yellow-orange appearance of tonsils
- Disease name?
- Gene?
- Inheritance?
- Lab finding?
- Why discoloration?
Tangier’s disease (orange tonsils = tangerine)
ABCA1 gene (adenosine triphosphate cassette transprter protein)
Autosomal recessive
Lab: high triglycerides, low HDL and LDL
Deposition of triglycerides (may also be fat-laden macrophages on bone marrow biopsy)
How does the short head of the biceps femoris help differentiat between a sciatic lesion and common peroneal lesion at the fibular head?
Spared in common peroneal lesion at fibular head
(Short head of biceps femoris supplied by peroneal nerve, but fibers leave while still part of the sciatic nerve)
(Note that within the sciatic nerve, peroneal portion more prone to injury as it is smaller, more lateral, and has less supportive tissue)
Sural nerve
Nerve roots
Source nerve
Area supplied
L4-S1, via tibial nerve (branches proximal to popliteal fossa)
Sensory to lateral leg and foot
Three terminal branches of tibial nerve
What does each do?
- Calcaneal:
Motor: none
Sensory: Heel - Medial plantar
Motor: aBduct great toe and flex toes other than pinky toe
a. ABductor hallucis
b. Flexor digitorum brevis
c. Flexor hallucis brevis
Sensory: Medial sole - Lateral plantar
Motor: aDduct great toe, flex and ABduct pinky toe
a. ABductor digiti quinti pedis
b. Flexor digiti quinti pedis
c. ADductor hallucis
d. Interossei
Sensory: lateral sole
Antibody associated with MMN (multifocal motor neuropathy)
Anti-GM1 (but not required for diagnosis, and does not predict response to therapy)
Primary treatment of MMN (multifocal motor neuropathy)
IVIG (steroids and PLEX not very effective)
(Can also add things likx ritux and cyclophosphamide)
Ulnar nerve muscles in the forearm
- Flexor carpi ulnarus (wrist flexion towards ulna)
- Flexor digitorum profundus to 4th/5th fingers
Which thenar muscles are innerated by the ulnar nerve?
ADductor pollicis (not actually part of thenar eminence)
Flexor pollicis brevis, deep part (superficial part is median like rest of thenar eminence)
(Opponens pollicis and aBductor pollicis brevis are median nerve.)
(Flexor pollicis longus (in forearm) is also median.
(ABductor pollicis longis (in forearm) is radial).
Nerve supply to hypothenar eminence
Ulnar nerve, deep motor branch
(Includes adductor digiti minimi, flexor digiti minimi, and opponens digiti minimi)
Nerve supply to dorsal and palmar interossei
Both ulnar nerve
Nerve supply to lumbricals
Median n: 1st and 2nd
Ulnar n: 3rd and 4th
Effect of S1 radiculopathy on motor, sensory, and reflex exam
Motor: Planarflexion and toe flexion weakness
Sensory: posterolateral lower leg and lateral foot
Reflexes: reduced ankle DTR
Ulnar claw hand: exam finding?
Elicited when fingers extended
Fingers 4/5 hyperextended at MCP and flexed at PIP and DIP (unable to extend)
Sign of benediction
Exam finding?
Cause?
Exam finding: when try to close hand, fingers 2 and 3 unable to close/flex
Due to high median nerve or anterior interosseous nerve lesion
Clinically, what differentiates ulnar neuropathy at the wrist (Guyon’s canal) from a more proximal lesion (e.g. medial malleolus)?
Motor: Proximal lesion with weakness of:
1. Flexor carpi ulnaris (wrist flexion towards ulna)
2. Flexor digitorum profundus (DIP flexion at digits 4 and 5)
Sensory: sensation to hypothenar eminence spared in wrist lesion
Radial nerve muscles spared in lesion at spiral groove
Triceps (branches leave before spiral groove)
Radial nerve muscles supplied by branches leaving between spiral groove and elbow
- Brachioradialis
- Extensor carpi radialis longus and brevis
(Extensor carpi ulnarus is also radial, but supplied by posterior interosseous nerve distal to elbow)
Radial nerve muscles supplied by posterior interosseous nerve, distal to elbow
- Adductor pollicis longus
- Extensor carpi ulnarus (wrist extension and adduction towards ulna) (Extensor carpi radialis is also radial, but leaves proximal to elbow)
- All finger extensors including thumb: extensor digitorum communis, extensor digiti minimi, extensor pollicis longus and brevis, extensor indices
Branches of radial nerve distal to elbow
- Posterior interosseous nerve (pure motor to aBductor pollicis longus, extensor carpi ulnarus, and finger extensors)
- Superficial sensory radial nerve (pure sensory to dorsolateral hand and dorsal digits 2/3)
Is wrist drop seen in radial nerve lesions:
1. Proximal to spiral groove?
2. From spiral groove to elbow?
3. Below elbow?
Seen in lesions proximal to elbow, but not distal
(Although extensor carpi ulnaris is affected below elbow, will not have overt wrist drop due to preserved extensor carpi radialis. However, will have weak adduction towards ulna).
How does SNAP on EMG distinguish radiculopathies from plexopathies?
Will be normal in radiculopathies but decreased in lesions distal to the DRG, including plexopathies
In a patient with a history of prior treated breast cancer including radiation, what can help clinically differentiate from radiation plexopathy versus carcinomatous invasion of brachial plexus?
What about on EMG?
Clinical: painful with carcinomatous invasion, painless in radiation plexopathy
EMG: Myokymic discharges associated with radiation plexopathy (recurring spontaneous firing MUAPs that fire in a repetitive burst pattern)
Antibody associated with Miller Fisher syndrome
GQ1B
What differentiates pronator teres syndrome from complete median neuropathy at the elbow?
Sparing of pronator teres (pronation)
(This is compression of median nerve as it passes between two heads of pronator teres, associated with repetitive forceful pronation)
Demyelinating polyneuropathy with progressive, asymmetric sensory and motor symptoms, associated with elevated CSF protein.
MADSAM: Multifocal acquired demyelinating sensory and motor neuropathy
Musculocutaneous nerve:
Roots?
Cord?
C5/C6
Lateral cord
Musculocutaneous nerve:
Muscles innervated?
Sensory?
Muscles:
1. Coracobrachialis (assists with shoulder flexion and extension)
2. Brachialis muscle (elbow flexor)
3. Biceps brachii (elbow flexion and also supination)
Sensory: Lateral forearm (lateral antebrachial cutaneous nerve) - no sensation to hand
Axillary nerve:
Roots?
Cord?
Roots: C5/C6
Posterior cord
Shoulder abduction muscle (and nerve) for:
First 30 degrees:
30-90 degrees:
> 90 degrees:
First 30: Supraspinatus (suprascauplar nerve off upper trunk)
30-90: Deltoid (axillary)
> 90: Trapezius (CN XI)
Axillary nerve:
Muscles innervated?
Sensory?
Muscles:
1. Deltoid (shoulder abduction, especially 30-90 degrees)
2. Teres minor (external arm rotation)
Sensory:
Upper lateral arm (via upper lateral brachial cutaneous nerve)
Genetic disease that can lead to painful distal small-fiber neuropathy, strokes, and is associated with skin findings including angiokeratomas
Genetic cause?
Fabry disease
X-linked lysosomal storage disease, alpha-galactosidase A deficiency
(Can also lead to GI issues, dilated cardiomyopathy and ESRD).
Rhomboid muscle: innervation and roots
C5
Dorsal scapular nerve (which is directly off C5, BEFORE brachial plexus)
Muscle involvement that distinguishes between upper trunk and C5/C6 root lesion
Rhomboid: involved in C5/C6 polyradiculopathy but spared in upper trunk lesion.
Innervated by dorsal scapular nerve, which is directly off C5.
Nerve injury causing winged scapula
Long thoracic nerve (weakness of serratus anterior which abducts the scapula, C5/6/7)
Which roots are compressed in neurogenic thoracic outlet syndrome?
C8 and T1
Pain and dysesthesias with patchy sensory and motor changes in thoracic and abdominal root territories
Common risk factor?
Thoracoabdominal polyradiculopathy
Often seen with longstanding diabetes
Group of hereditary neuropathies with primarily sensory and autonomic involvement
Hereditary sensory and autonomic neuropathy (HSAN)
AD HSAN that presents in young adulthood, with pain/temperature specific sensory loss and hypohidrosis
HSAN1 (due to serine palmitoyltransferase mutation, involved in sphingolipid synthesis)
AR HSAN that presents in infancy with severe sensory loss leading to risk of injury, with less impressive autonomic symptoms.
HSAN2
AR HSAN with predominanc autonomic feature, with presentation in inphancy with dysautonomia (dysphagia, vomiting, recurrent infections, labile BP, hyperhydrosis), with later onset of sensory neuropathy.
HSAN3 (aka Riley-Day syndrome, IKAP mutation that leads to abnormal mRNA splicing)
AR HSAN with congenital insensitivity to pain and cognitive delay, as well as anhidrosis
HSAN4 (mutation in TRK for nerve growth factor, NTRK1)
AD disorder presenting with severe burning and erythema of the distal extremities triggered by hot or cold exposure (asymptomatic between episodes)
Primary erythromelalgia (due to SCN9A mutation, leads to DRG hyperactivity)
(Secondary erythromelalgia is similar symptoms due to e.g. polycythemia vera or SLE)
Brachial plexus: which cord(s) does each nerve arise from?
Axillary
Musculocutaneous
Median
Radial
Ulnar
Axillary: Posterior
Musculocutaneous: Lateral
Median: Medial and Lateral
Radial: Posterior
Ulndar: Medial`
Brachial plexus: which trunk(s) give rise to each cord:
Lateral? Medial? Posterior?
Lateral: Anterior divisions of superior and middle trunks
Medial: Anterior division of inferior trunk
Radial: Posterior divisions of all 3 trunks
Syndrome with episodes of GI symptoms followed by neurologic symptms which may include autonomic instabillity, neuropsychiatric symptoms, seizures, and subacute predominanlty motor neuropathy
AIP (acute intermittent porphrya
Lesion with posture held with arm close to body, internally rotated, with flexed fingers and wrist, with weak arm abduction and flexion.
Erb’s palsy - upper trunk lesion (can be seen with birth injury and accidents)
Antibodies associated with AMSAN?
AMAN?
AMSAN: GM1, GM1b, GD1a
AMAN: GM1, GM1b, GD1a, also GalNac
Which interossei aBduct fingers? Which aDduct?
Dorsal ABduct (DAB)
Palmar ADduct (PAD)
Localization of abduction of 5th digit at rest
Ulnar neuropathy (Wartenberg’s sign)
When the patient tries to forcefully hold a piece of paper between the thumb and index finger, the thumb flexes. What is this a sign of?
Ulnar neuropathy (Froment’s sign) (Due to thumb adductor weakness)
When asked to make an “OK” sign, unable to flex the DIP of thumb and index finger to touch fingertips together, so thumb is extended and the finger pads touch, so the “O” is not round. What is this a sign of?
Anterior interosseous neuropathy (due to weakness of flexor pollicis longus and flexor digitorum profundus to 2nd digit (also affects 3rd digit, and pronator quadratus)
(Branch of median nerve)
Neuropathies associated with retinitis pigmentosa (4)
- Refsum’s disease (phytanic acid accumulation)
- Myoneurogastrointestinal encephalopathy
- NARP: Neuropathy, ataxia, and retinitis pigmentosa syndrome
- Abetalipoproteinemia
Syndrome of neuropathy, ataxia, RP, and acanthocytes on peripheral smear?
Abetalipoproteinemia
