Clinical Neurophysiology Laboratory

The Clinical Neurophysiology Laboratory places its expertise at your service by working in close collaboration with:

Our Neuromuscular Disease Reference Centre (CRMN), to enable the diagnosis and monitoring of rare diseases such as:

• Neuropathies of immune origin (Guillain–Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP))
• Amyloidosis
• Motor neuron diseases such as Charcot disease, also known as amyotrophic lateral sclerosis
• Neuromuscular junction disorders such as myasthenia gravis or Lambert–Eaton syndrome
• Periodic paralyses and other muscle diseases (myopathies such as myositis, dermatomyositis, myotomies, …), 

Various departments, such as neurosurgery, the endocrinology department, internal medicine, oncology, rheumatology, orthopaedics, and gastroenterology, for common conditions regularly requiring examinations in our laboratory:

• Polyneuropathies, polyneuritis or neuropathies related to diabetes, vitamin deficiencies, chemotherapy toxicity, …
• Sciatica, radiculopathies and plexopathies
• Carpal tunnel syndrome or other nerve compressions.

We also provide our expertise for monitoring these conditions, in close cooperation with all these departments whenever necessary.

We also perform evoked potential tests, which assess the function of the neural structures associated with our senses (somatosensory, visual and auditory) or with motor pathways. We use these tests to investigate conditions with a complex diagnosis, such as:        

• Multiple sclerosis
• Cervical myelopathy,
• Myelitis,
• Syringomyelia,
• Amyotrophic lateral sclerosis
• … 

The tests most frequently performed in this department are as follows:

Nerve conduction velocity testing

Diseases affecting the peripheral nerves may cause a slowing of the conduction velocity of nerve impulses, as well as a reduction in the amplitude of responses in the muscles activated by these nerves, or a reduction in the amplitude of the electrical response of the nerves that carry sensory information. To record these responses, the doctor will place adhesive electrodes either on a muscle activated by the nerves being studied or along the path of a sensory nerve. The nerves being studied are most often activated using a stimulator that delivers an electrical current whose intensity is gradually increased to obtain the largest possible response. To ensure that this test is performed properly, please keep your hands and/or feet as warm as possible (for example, by wearing boots or gloves in winter and closed shoes during the other seasons, etc.). Also avoid using oily or moisturising ointments, as these interfere with contact between the electrodes and your skin.

Electromyography (EMG) 

This test involves inserting a fine needle into the muscle being examined. The needle records the electrical activity produced by the muscle fibres when the muscles are activated or when they are at rest and fully relaxed. This analysis can detect abnormalities related to impaired nerve function (neurogenic involvement) or muscle function (myopathic involvement). Please remember to tell us if you are taking anticoagulant medication, as this test involves a needle puncture.

Repetitive stimulation

When a motor nerve is activated, the electrical impulse travels through the nerve ending that is in contact with the muscle. This specialised structure is called the neuromuscular junction. A neurotransmitter (acetylcholine) is released, enabling the muscle to be activated. Certain conditions, such as myasthenia gravis and Lambert-Eaton syndrome, cause dysfunction of this neuromuscular junction, preventing normal activation and resulting in abnormal muscle fatigue.

Evoked potentials

These techniques involve stimulating the sensory organs to assess the function of the specialised neural structures responsible for transmitting information related to touch, hearing and vision, using electrical shocks, headphones or a screen, respectively. These stimuli activate different structures of the nervous system. Electrodes placed at specific points on the scalp, neck and limbs record electrical activity, making it possible to analyse the time required for nerve impulses to travel through the activated structures. Somatosensory evoked potentials assess sensitivity using stimulation—most commonly an electrical shock—of the sensory nerves in the upper or lower limbs. Auditory evoked potentials are recorded using headphones that produce sounds which activate the inner ear and generate electrical currents in the auditory pathways. Visual evoked potentials are recorded while a screen displays checkerboard patterns alternating between white and black squares. This visual stimulation activates the retinal cells, optic nerve and specialised brain structures involved in processing visual information, ultimately activating neurons in the occipital cortex. 

Motor evoked potentials

This test assesses the motor pathways by stimulating the motor neurons in the cerebral cortex using a magnetic field produced by a current delivered to an electrical coil placed on the head. This technique produces painless stimulation through the skull or at the cervical or lumbar region. The resulting response is recorded by electrodes placed on the muscles of the hands or legs. Please remember to tell us if you have epilepsy or if you have any implanted metal devices in your body (pacemaker, cochlear implant, etc.) or retained metal fragments (bullets, etc.).