Division of Neurology
Diagnostic services are available at all four sites of the Hamilton Health Sciences: McMaster, Chedoke, Hamilton General and Juravinski divisions, as well as St. Joseph's Healthcare.
EEG test procedure
- Length of test: 60-90 min. (depends on patient compliance and test type e.g. Sleep deprived EEG vs. Routine EEG).
- Definition: electroencephalograph: surface recordings of electrical activity of the brain.
- Measure patient's head with measuring tape and wax pencil according to an internationally recognized 10/20 system.
- Prep skin surface at premeasured sites on scalp with a mild abrasive cream (we do not break the skin).
- Apply electrode cream into each electrode cup and place on designated site with cotton ball or paper tape.
- Wrap head with cling as required especially: pediatric population.
- Patient lies on bed with room lights off to create relaxed atmosphere.
- Minimum standard length of EEG recording is 20 min.
- Success of EEG depends on ability of patient to relax as muscle activity and/or artifacts created from movement blocks ability to read brain wave activity.
24 hour EEGs
- Surface recording of electrical activity of the brain recorded on a digital recorder over a 24 hour period for longer quantitative assessment of patients' neurological status.
- Patient wears apparatus home, maintaining a diary of activities of 24 hr. period.
- Patient signs a loan agreement for use of the equipment.
- Pre-requisite: a routine or sleep deprived EEG recorded at m.u.m.c. That becomes the baseline and reference to technologist scanning the 24 hr. EEG.
NB: electrode application same for skin prep and measuring of electrode placements.
Difference: Electrodes adhered to scalp with an adhesive glue called collodion and removed with a non-acetone base solution (mavidon)the next day.
Some medical reasons for having an EEG
- Head injury
- Delayed development/ prematurity
- Stroke/ T.I.A.s
- Brain tumour, a.v. Malformation, aneurysm
- Psychological disorders i.e. depression, manic/obsessive disorders.
- Alzheimer's disease / dementia
- Post M.V.A.: assessment of neurological status
- Learning/behaviour problems including autism, ADD., ADHD., Tourette's
- Jacob Creuzfeld disease
- Herpes encephalitis
- Meningitis (bacterial/viral)
- Encephalitis (viral/herpes)
Role of an EEG Technologist
- Take clinical history & medication profile
- Explain & prepare the patient for the procedure including electrode set up
- Observe patient behaviour
- Instruct patient how to perform certain tasks
- Determine or abort activation procedures i.e: photic stimulation & hyperventilation
- Ongoing monitoring of EKG routinely and respiration as needed
- Technologist needs to be competent in neurophysiology, recognizing normal vs. abnormal electrical activity & artifacts
- Record any clinically significant observations for physician, who later reviews and interprets the EEG data
- Read final report of their specific patients prior to mailing to verify information on the report
EMG test procedure
- Pre-requisite: avoid use of body creams, oils or lotion that coats the skin surface and impedes good contact with recording electrodes during the EMG examination
- Description: an EMG is the study of the responses of nerves and muscles to small electrical stimuli
Nerve conduction study part of the EMG
- Different areas of the arm and/or leg are measured with a non-toxic skin pencil and wiped with an alcohol swab.
- Surface adhesive electrodes are applied to the muscle innervated by the nerve being assessed.
- Patient receives shock-like sensations delivered at different sites along the nerves that run up and down the arm/leg for the nerve conduction part of the test.
- These shocks can make the limb twitch very briefly.
Electromyography part of the EMG
- The electromyography part of the test is performed by a physician and involves the insertion of very fine hair-like needle (similar to an acupuncture needle) into the different muscle sites at the discretion of the physician (there are no injections through the needle).
- The responses from the needle in the muscle is heard on an amplifier and studied simultaneously on a monitor by the physician while the muscle is at rest and when the patient is asked to contract the muscle.
Plus consult: the physician either during or at the completion of the EMG study continues the visit with a consultation, which includes an extensive history taking and physical examination.
Additional diagnostic testing as part of the Neuromuscular Clinic
- Muscle biopsy: minor surgical procedure that requires a small piece of muscle being taken from examination under a microscope to detect the presence of neuromuscular disease.
- Skin biopsy: minor surgical procedure that requires a small piece of skin sample being taken for examination under a microscope to detect the presence of neuromuscular disease.
- Forearm ischemic test (FIT.): to assesses the ammonia and lactic acid levels in the blood following a specified period of exercise. Used to detect the presence of neuromuscular disease.
- Single fibre test: to determine the presence of a neuromuscular transmission disorder.
Some medical reasons for having an EMG
- Familial/hereditary neuropathy
- Diabetic neuropathy/ peripheral neuropathy
- Bell's palsy, carpal tunnel, cervical root lesions, hypotonia, low back pain
- GuillianBarre syndrome
- Myaesthenia gravis
- Muscular dystrophy
- Post polio syndrome
- Foot drop
- Whip lash
- Charcot Marie tooth
- Vincristine neuropathy (any neuropathies as a result of chemo)
- Traumatic nerve/muscle injuries e.g. Brachial plexus, spinal cord injuries.
- Radiculopathies from whiplash etc.
EVPs test procedures
- Length of test: 20 min. Each (time can vary in pediatric population).
- Description: measures variability of brain function in visual, auditory and somatosensory pathways.
Important: Interpretation is based on how long it took for the stimulus to travel through the pathway being tested. Results print out on grid paper over a predetermined timebase with latency measures of components along the pathway. The values of the latency as well as the shape of the response are very important to the interpretation of the EVP Test.
- Electrode application: same as EEG, only fewer electrodes used specific to the anatomical area being tested.
- Visual EVP: Patient sits in chair testing one eye at a time. They watch a repetitive pattern on a monitor wearing corrective lens if required.
- Auditory EVP: Patient lies on bed wearing earphone. Hearing threshold is determined first by technologist. Sound turned up according to hearing threshold to adequately stimulate hearing nerve.
- Somatosensory EVP (arms or legs): Patient's median nerve at wrist or peripheral nerve behind knee is wiped with alcohol. Surface stimulator is placed on nerve. Technologist applies a small electric shock to trigger a twitch in hand or foot in distribution of the specific nerve pathway. Patient needs to be relaxed.
Some medical reasons for having Evoked Potentials
- Grave's disease (thyroid condition)
- Multiple sclerosis (m.s.)
- B12 deficiency
- Pseudotumour cerebri
- Retinal hemorrhages
- Birth asphyxia
- Cortical blindness
- Eye injury
- Bell's palsy
- Dizziness meningitis
- Meniere's disease
- Acoustic neuroma
- Sudden decreased hearing
- Increased intracranial pressure
- Brain death
- Unexplained loss of consciousness
- Brainstem stroke
- Numbness/tingling of limbs
- Bladder dysfunction
- Vincristine neuropathy
- Work related injury
- Neck injury
- Motor vehicle accident (m.v.a.)
Multiple modality EVPs
- VEP, BSP, CSSEP commonly requested as a set for many of the above medical problems.