To Determine Diagnosis

A nerve disorder can be from the brain, anterior horn cell, spinal root, plexus, peripheral nerve(s), neuromuscular junction, and/or the muscle.

Deciphering between central versus peripheral nervous system lesions

Neurological symptoms resulting from stroke, brain injury, spinal cord injury, multiple sclerosis, and other central processes appear normal on electrodiagnostics

Neurological symptoms arising from disease of the anterior horn cells appear abnormal on electrodiagnostics
Presently, we do not manage motor neuron disease. If this is highly suspected, we refer to the appropriate neuromuscular experts

Patients typically complain of very severe pain with true root avulsions. This can be seen with the presence of a pseudomeningocele on MRI of the cervical spine
Electrodiagnostics can assess the completeness of the root avulsion, if present

Electrodiagnostics rarely produce false positive results, whereas imaging studies are notorious for demonstrating incidental abnormalities
Electrodiagnostics help determine the severity of a radiculopathy by quantifying axonal damage, if present
In this way, electrodiagnostics aligns the patient history, physical examination, and imaging to help determine whether the apparent pathology is of clinical significance
Reasons why nerve conduction studies may be "normal"
- Most radiculopathies are sensory in nature, and with pathology being proximal to the dorsal root ganglion (DRG), nerve conduction studies appear normal as Wallerian degeneration proceeds centrally
- An exception to this rule is an L5 radiculopathy, where the DRG is within the intervertebral foramen, but this is rare
Reasons why needle EMG studies of the muscle may be "normal"
- The injury is affecting purely sensory nerves, and so the axons of motor neurons are intact
- The injury is purely demyelinating, and so the signaling of motor neurons is intact. A complete conduction block, however, would demonstrate reduced recruitment of motor units
- The injury is acute, and so a pattern of muscle involvement proximal to distal cannot be demonstrated
- The section of muscle sampled may be spared given input from other roots
- The entire muscle is spared as the nerve fascicle supplying it is unaffected at the root-level

Electrodiagnostics can help identify specific nerves involved and non-compressive lesions where imaging may be normal
Plexopathies can occur for many reasons, from acute trauma, compression, even systemic disease (e.g. diabetes, autoimmune)
Presently, we do not assess plexopathies in babies as a result of birth trauma

Common examples include
- Median nerve at the wrist (carpal tunnel syndrome)
- Ulnar nerve at the elbow
- Sciatic nerve near the low back (“sciatica”)
- Fibular nerve at the knee (“drop foot”)

Common causes include diabetes, medications, and nutritional deficiencies
Electrodiagnostics helps categorize PN into primarily demyelinating, mixed, or axonal categories. It can further separate it into uniform, segmental, or length-dependent processes. This may affect only sensory, only motor, or both types of nerves. Standard electrodiagnostics cannot detect a predominately small fibre process.
Presently, we do not offer nerve biopsies for small fibre testing, but this is often not required for diagnosis.

Diseases of the neuromuscular junction include myasthenia gravis and Lambert-Eaton myasthenic syndrome
Presently, we do not offer repetitive nerve conduction testing or single fibre EMG. If this is highly suspected, we refer to the appropriate neuromuscular experts

Needle EMG can identify muscle membrane irritability and disrupted motor units
Presently, we do not offer perform muscle biopsies. If this is highly suspected, we refer to the appropriate neuromuscular experts