Unit III Flashcards
What section supports EMG/NCS in the KY state practice act?
KRS 327.10
“…evaluations performed to determine…nerve and muscle function including subcutaneous bioelectrical potentials…”
T/F: Medicare recognizes and reimburses EMG services performed by ABPTS certified and non-certified clinicians
False; only certified PTs are reimbursed for EMG testing
What is the primary goal of rehabilitation?
optimization of motor control
What is a motor unit?
anterior horn cell > nerve root > plexus > nerve (proper) > NMJ > muscle fibers innervated by nerve
What is the relationship between lateral ankle sprains and the tibialis posterior?
86% of patients with grade III demonstrated denervation of the gastrocnemius/soleus complex; patients have difficulty eccentrically lowering their foot to the ground
What is the relationship between proximal shoulder dislocations and proximal humeral neck fractures and EMG changes?
54% of patients demonstrated EMG changes following proximal humeral neck fractures
What is the effect of NMES on denervated muscles?
delays reinnervation if applied too soon
How does EMG testing assist clinical decision-making?
- diagnosis
- prognosis
- motor unit recruitment
- aggressiveness
- timeframes
- refer/triage
- when the patient is safe to return to sport, work, etc.
What are the three important physiology principles?
- separation of charge
- “all-or-none” depolarization
- volume conduction
Resting membrane potential is maintained by:
- semi-permeable membrane = passive flow of ions
2. sodium-potassium pump (active transport)
What are the three functions of myelin?
- speeds up conduction
- conserves energy
- conserves space
What are the three categories of nerve injury described by Seddon in 1945?
- neuropraxia
- axonotmesis
- neurotmesis
Neuropraxia
transient loss of myelin
Axonotmesis
degeneration/injury to the axon; Wallerian degeneration occurs
Neurotmesis
injury to the epineurium nerve sheath
Signs of denervation
- positive sharp waves
- fibrillations
What changes occur in the cell body following denervation?
- central chromatolysis
- nissl substance gets darker
Signs of nerve regeneration are indicated by:
polyphasic voluntary motor units
Re-innervation
- nodal sprouts
- terminal sprouts
- Early (nascent polyphasic potentials and RFR)
- Late (RFR and giant complex polyphasics)
Sources of error associated with EMG instrumentation
- dirty electrodes
- broken lead wires
- poor ground
- too much electrode gel
- fluorescent lights
- cell phone signal
- incorrect connection of electrodes at pre-amp box
- power line load
- the motor of high-low tables
Segmental demyelination
- nerve conduction study
- abnormal almost immediately after onset
- mild to moderate compression, auto-immune disorders, etc.
Axonal degeneration
- needle EMG
- 21 days post-onset (7-14 days for paraspinals)
- severe compression, ischemia, inflammation
EMG testing principles
- examine motor and sensory when possible
- test several segments of nerve suspected
- may need to test upper and lower limb nerves
- test when likely to obtain the optimal diagnostic yield (≥21 days)
Influencing factors
- upper vs. lower extremity
- age = decreased 10% per decade after 60 YOA
- temperature
- anatomical anomalies
NCS abnormalities
- slowed latency = myelin issue
- reduced amplitude = axonal issue
- attenuated duration = sawtooth appearance
- slowed conduction velocity
- absent response
Repetitive stimulation will demonstrate a ___ abnormality
neuromuscular junction
Normal NCS
≤ 4.0 milliseconds
Treatment for mild CTS
- prolonged DML = 4.0-5.4
- observation, conservative Rx
Treatment for moderate CTS
- prolonged DML = 5.4-7.2
- conservative modalities first; surgery later if needed
Treatment for severe CTS
- prolonged DML = >7.2
- surgery strongly recommended
- increased fibrillations, polyphasic VMUs, or electrical silence
Treatment for severe CTS
- prolonged DML = >7.2
- surgery strongly recommended
- increased fibrillations, polyphasic VMUs, or electrical silence
Steps of EMG testing
- insertion (300 milliseconds)
- Rest
- Minimal contraction
- Maximal contraction
Abnormal EMG findings at rest
- 1+ = induced by electrode movement
- 1-2+ = spontantoue appearance
- 3+ = many spontaneuous potentials
- 4+ = screen filled with abnormal potentials
Reduced insertional activity
- resistance to needle movement in tissue
- associated with chronic denervation - fibrotic degeneration, fat infiltration
- “woody” feel
Increased insertional activity
- after cessation of needle movement
- associated with myotonic disorders, myogenic disorders, and denervation
Smaller than normal amplitudes may be the result of:
axonal degeneration or myopathy
What is the most sensitive imaging study for spinal stenosis?
CT myelography
Typical nEMG findings in lumbar spinal stenosis
- early = little if any abnormality
- over time = conduction block, axonal loss, demyelination or re-myelination
- first change may be absent H-reflexes
- Bilateral findings in up to 50-87%
Non-invasive quantitative EMG
- patient follow-up
- children
- measure response to Rx
Rationale for EMG biofeedback
- adjunct to a total rehab program
- control of motor unit activity with EMG ( recruitment, relaxation)
- contraindications (gel, tape skin irritations, and metabolic confusion)
Recruitment EMG Biofeedback
- peripheral nerve injury
- muscle weakness (post-immobilization, joint surgery, deconditioning)
- muscle transfers
- postural control
Relaxation EMG Biofeedback
- stress-related ANS arousal
- pain (migraine, tension headaches)
- spasticity
- rigidity (i.e. adult onset torticollis)
EMG Biofeedback Goals
- increase amplitude
- increase the total number of MUs firing
- increase frequency of MU firing
- restore joint movement
- return motor unit recruitment to normal to protect and move joint properly
Appropriate patient selection for EMG biofeedback
- Does patient have motor impairment?
- Does motor impairment seem likely to benefit from biofeedback information?
- Does patient demonstrate the ability for voluntary control?
- Is patient sufficiently motivated and cognitively aware to use feedback info?
Appropriate patient selection for EMG biofeedback
- Does patient have motor impairment?
- Does motor impairment seem likely to benefit from biofeedback information?
- Does patient demonstrate the ability for voluntary control?
- Is patient sufficiently motivated and cognitively aware to use feedback info?
Myopathy will demonstrate what on EMG?
smaller than normal amplitudes, highly polyphasic, short duration MUPs
Normal MUP Duration
3 to 12 msec
According to Haig et al, what is the most significant predictors of LSS?
paraspinal mapping and absent tibialis H-reflex
