Clinical Neurophysiology Flashcards
What is the purpose of nerve conduction studies / electromyography?
Investigates problems of peripheral nerves and muscles
EMG is used in neuromuscular disorders and disorders of motor control
Nerve conduction studies are used in conjunction to measure the ocnducting function of nerves (unless it is a purely myopathic condition)
When is needle EMG and NCS indicated?
Needle EMG and NCSs are typically indicated when there is pain in the limbs, weakness from spinal nerve compression, or concern about some other neurologic injury or disorder
What are sensory studies?
Similar technique stimulating the sensory nerve fibres in the fingers allows measurement of sensory and motor function separately.
What is the purpose of EEG?
Electrical activity within the brain, investigate epilepsy and states of altered consciousness
What is the purpose of evoked potential tests?
Measures the time taken for nerves to respond to stimulation. The size of the response is also measured.
What are the two measurable factors in nerve conduction studies?
Conduction velocity and amplitude
What diseases can EMG aid in the diagnosis of?
Needle EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.
What does wasting FDI stand for?
First dorsal interosseous muscle wasting - muscle you can feel between thumb and first finger
What syndrome is wasting FDI a part of?
Part of split hand syndrome
What is split hand syndrome?
Neurological syndrome in which the hand muscles on the side of the thumb (lateral, thenar eminence) appear wasted, whereas the muscles on the side of the little finger (medial, hypothenar eminence) are spared.
Anatomically, the abductor pollicis brevis and first dorsal interosseous muscle are more wasted than the abductor digiti minimi
What causes split hand syndrome?
Lesions affecting branches of the ulnar nerve
Spinal root lesion affecting the anterior horn of C8-T1 - C8 radiculopathy
What evidence would suggest that the split hand syndrome is a result of ulnar neuropathy?
A slow onset and a lack of pain or sensorial symptoms are arguments against a lesion of the spinal root or plexus brachialis.
What woud an electrophysiology study on the arm show in
- Ulnar neuropathy
- C8 radiculopathy
- Slowing across elbow, evidence for conduction block at elbow, small sensory response from ulnar nerve - due to demyelination and conduction block
- Small but not slowed motor response, normal sensory response (becaue cell ganglion is still intact?)
What does myasthenia graves present with?
What is the underlying pathology in myasthenia graves?
Antibodies bind to post synaptic ACh receptor which blocks Ach from being able to bind. MG gets worse when exercising due to the simple fact that when you exercise you use more muscle. More Ach wanting to bind to blocked receptors… they can’t hence why exertion makes it worse.
What is the finding of Myasthenia Graves on SF EMG? Why?
Jitter
The needle is positioned to record from two fibres within the same motor unit, there is normally little variation in the time of firing between the two fibres. However in the NM junction in disease, the tight relationship between the two muscle fibres is lost and results in a jitter
