Tibial and fibular (peroneal) motor nerve conduction studies (NCS) are used in most lower limb electrodiagnostic evaluations and should be mastered early. This chapter discusses lower limb motor studies. The tibial nerve innervates the muscles of the posterior leg and then divides posterior and distal to the medial malleolus into the medial and lateral plantar nerves innervating the sole of the foot. The deep fibular nerve innervates the extensor digitorum brevis. The motor study may be abnormal with any injury of the sciatic, tibial, or medial plantar nerve. The Normative Data Task Force of the American Association of Neuromuscular and Electrodiagnostic Medicine identified only one fibular motor nerve study and two tibial motor nerve studies in the literature that were considered suitable as a resource for NCS metrics.

Limb and periscapular muscle weakness is the most common presentation of a person with a brachial plexopathy. Pain is a more variable symptom and is typically associated with trauma, neoplasm, and brachial neuritis. Postoperative plexopathies, rucksack-associated neuropathies, and radiation-induced neuropathies may present with minimal pain. In lower trunk injuries, patients may present with Horner syndrome. All evaluations should start with a thorough history followed by a complete neurological examination. Winging of the scapula may occur with brachial plexus lesions; the static and dynamic positions of the affected scapula may be associated with specific nerve lesions. The differential diagnosis of a patient presenting with upper limb pain and weakness is broad and includes other processes such as nerve root avulsions, radiculopathies, myelopathies, motor neuron disease, and peripheral nerve entrapments. This chapter discusses anatomy, classification, anatomic variants, and electrodiagnostic approach of branchial plexopathy.

High frequency ultrasound is an excellent complimentary modality to electrodiagnostic techniques. It provides detailed anatomic correlation to the physiologic information obtained with electrodiagnosis. It has many advantages for assessing neuromuscular conditions over other imaging modalities. It can be used to assess pathology in peripheral nerves, mimicking neuromuscular conditions and muscles diseases. It can also be used to safely guide electromyography needle insertion in vulnerable regions and assist with anatomic localization of challenging nerves and muscles. This chapter discusses the uses of ultrasound with electrodiagnosis. It list out the advantages of using ultrasound with electrophysiologic techniques and over other imaging techniques. The chapter provides the principles of imaging peripheral nerves with ultrasound. It also provides imaging strategies to improve visualization of peripheral nerves and principles of imaging muscle for neuromuscular assessment with ultrasound.

This chapter discusses general considerations for performing lower limb sensory studies. Given the nature of sensory responses, focus closely on obtaining supramaximal stimulation while ensuring avoidance of stimulus artifacts and co-stimulation of nearby nerves. Sensory nerve action potential (SNAP) should be reproducible in amplitude and latency across multiple stimuli. Eliciting a SNAP may be challenging in patients with pedal edema, excess fatty tissue, or in those who are older in age. Most studies are performed antidromically. A SNAP is biphasic or triphasic. Both onset latency and peak latency can be measured/ compared. Side-to-side comparison is helpful. Lower extremity nerve conduction studies are useful for evaluating for neuropathic lesions involving and distal to the dorsal root ganglion. The chapter discusses the anatomy and nerve conduction study of sciatic nerve; sural nerve; superficial fibular (peroneal) nerve; saphenous nerve; and lateral femoral cutaneous nerve respectively.

This chapter discusses motor unit action potential analysis. A motor unit action potential (MUAP) is the electromyographic response that results from the discharge of all the muscle fibers that are innervated by a single motor neuron. The size and shape of an MUAP can be described in terms of amplitude, duration, phasicity, and stability. The size and shape of MUAPs are dependent on the size, number, and functional state of muscle fibers innervated by a single motor neuron. Firing characteristics and recruitment of motor units can also be quantified, enabling identification of different patterns of pathology of the neuromuscular system. The chapter provides a brief description on motor unit morphology and changes in MUAP characteristics and morphology in diseases such as myopathies; denervation and reinnervation.

F-waves and H reflexes are known as late responses. Late responses evaluate the entire nerve from root to the neuromuscular junction. Routine nerve conduction studies (NCS) only test the distal segment of peripheral nerves. F-waves represent the antidromic motor responses obtained following electrical stimulation of a peripheral nerve. They are most useful when the distal segment is normal and the proximal segment is abnormal. Measuring a longer segment allows detection of a proximal or diffuse problem, such as a demyelinating process. The F response is not an actual reflex; a reflex is a response that goes through a sensory component, synapses in the central nervous system, and then travels back down into the motor pathway. With F-waves, the pathway is from motor fiber to cell body and back to motor fiber.

Radiculopathy, a disorder of the spinal nerve roots, is one of the most common diagnoses referred for electrodiagnostic (EDX) evaluation. It is important to remember that an electromyography/nerve conduction study is an extension of the history and physical examination. EDX studies should be ordered when the diagnosis remains unclear. EDX studies functionally assess the nerve, localize the lesion, and exclude other neurological causes of limb pain, sensory changes, and weakness. Radiculopathy can be an axonal or demyelinating disorder affecting nerve fibers at the level of a single root or spinal nerve. The anterior (motor) root, posterior (sensory) root, or both may be affected. Pathology in the spinal nerve is less common. This chapter discusses lumbosacral radiculopathy and its clinical presentation, anatomy and electrodiagnostic approach.

Femoral nerve injuries are uncommon, and thus easily missed. The femoral nerve innervates the hip flexors and knee extensors, which are key muscle groups in ambulation. The saphenous nerve is a distal extension of the femoral nerve. The most common causes for femoral nerve injury are iatrogenic from surgery, particularly abdominal and pelvic, related to lithotomy positioning or compression from retractors. History of present illness and physical examination are important components in electrodiagnostic assessment as they help the examiner to localize the lesion. The chapter discusses the anatomy of femur: inguinal ligament; femoral triangle (Scarpa triangle); and Hunter canal. It provides a brief description on electrodiagnostic approach for femoral neuropathy. Nerve conduction study can be quite uncomfortable due to nerve depth.

Needle electromyography (EMG) is usually performed after nerve conduction studies have been completed, but can be performed first or by itself depending on the clinical indication. No electrical stimulation is used with EMG; the needle is simply a tool to measure the electrical activity in the muscle. The muscles that will be evaluated are chosen carefully based on the differential diagnosis. The examiner should evaluate only the minimum number of muscles that are necessary to do an adequate study, as examining more muscles may make the test more uncomfortable for the patient. It is important to begin with an environment that is conducive to performing a study. Whenever possible, this includes a comfortable, quiet, interference-free environment, which is stocked with the appropriate supplies to limit interruptions. This chapter discusses basic EMG technique. It focuses on reducing anxiety and discomfort of the needle examination. The chapter provides protocol for procedure.

Ulnar neuropathy may result from nerve compression as it traverses along the medial aspect of the arm, crosses the elbow, through the forearm, or passes through the wrist. This chapter discusses ulnar neuropathy at the elbow and its clinical presentation. It also provides a brief description about ulnar nerve anatomy. The ulnar nerve is the terminal extension of the medial cord of the brachial plexus which is derived from the C8 and T1 nerve roots. C7 can also contribute from contribution of the median nerve (lateral cord decussating with medial cord). The chapter then discusses the electrodiagnostic approach. Sensory abnormalities along the distribution are helpful in identifying the location of injury. Motor conduction studies are especially useful in identifying pathology at the elbow which is the most common area of injury.