Clinical neurophysiology

Clinical neurophysiology is a physiological specialty based on the knowledge of neurosciences, it studies the function and dysfunction of the nervous system produced by diseases of the brain, spinal cord, peripheral nerve, muscle and organs of the senses, using neurophysiological and imaging techniques to measure the activity of the nervous system. The data obtained, when interpreted in the clinical context of the patient, makes it possible to diagnose or help diagnose the neurological process, as well as to quantify, monitor and assess its evolution. Clinical Neurophysiology also includes physiological methods for the treatment of neurological and psychiatric diseases".

History

Although the beginnings of basic neurophysiology can be found in the experiments on “animal electricity” by the Italian physician and physicist Luigi Galvani (1737-1798), the development of Clinical Neurophysiology has its beginnings with the British physiologist Edgar Douglas Adrian (1889-1977), who incorporated the method and language of basic-experimental neurophysiology into clinical practice, and the American-born English physician Gray Walter (1910-1977), who introduced engineering methodology with clinical-diagnostic purposes.

Clinical Neurophysiology began to be implemented in hospital care activity after the Second World War, with the era of transistors. It arises from the multidisciplinary conjunction of doctors and physicists to achieve the recording and interpretation of physiological activities, both at the level of the central and peripheral nervous systems. This generated progress in the knowledge of the normal and pathological functioning of the nervous structures and made it possible to establish electroclinical correlations with the various pathologies. It should be noted that, in its beginnings, Clinical Neurophysiology could be reached from both Medicine and Physics, in both cases completing complementary training, in the case of doctors in the area of physics, and in the case of of physicists in the area of medicine.

The first Congress of Clinical Neurophysiology, promoted by William Gray Walter and Denis Hill, was held in London in 1947 with the aim of standardizing electroencephalography techniques that had begun to be developed before World War II. In it Lord Adrian was elected as the first President of the Society. In this congress, Spain participated with the neurosurgeon Sixto Obrador, a great promoter of Clinical Neurophysiology in Spain.

It is also based on the studies of the Spanish physician and histologist Santiago Ramón y Cajal (1852-1934) who, in 1891, postulated the Law of dynamic polarization of neurons. This Law indicates that the currents, which conduct bioelectrical information in the nerve cells (neurons), flow from the dendritic ramifications towards the body of the neuron, where said information is processed, and from this towards the terminal ramifications or axons, to contact through the synapse with one or more other neurons. In addition, Ramón y Cajal discovered that the nervous system is not a continuous neural skein but a network of nerve cells exquisitely interconnected with each other, while maintaining their individuality.

Diagnostic techniques used in clinical neurophysiology

The various techniques currently used are grouped into broad areas:

Electroencephalogram (EEG)

The EEG was the first to be developed. It consists of recording cerebral bioelectric activity in baseline conditions of rest, wakefulness, sleep, and during various activations (usually hyperventilation and intermittent light stimulation). It allows the diagnosis of diseases such as epilepsy, encephalopathies, coma, diagnosis of brain death and others. Within this section are also related techniques such as brain mapping and magnetoencephalography.

Electromyography

Electromyography is a set of techniques that allow studying the function of peripheral nerves, nerve roots, neuromuscular junction or muscle. They analyze voluntary muscle activity and/or motor and sensory nerve conductions in various nerve segments. Within this section there are also related techniques such as the exploration of the vegetative system.

Evoked Potentials

Evoked potentials assess the responses of the nervous system to specific known and normalized sensory stimuli. Light stimuli are used to assess the visual pathway, acoustic stimuli to assess the auditory pathway, electrical stimuli to assess the sensory pathway, etc. Within this section there are also related techniques such as electroretinography, electrooculography, electrocochleography and otoacoustic emissions.

Sleep disorders, polysomnography and respiratory polygraphy

Polysomnography consists of recording brain bioelectric activity simultaneously with various cardiorespiratory variables and muscle activity that allow us to assess the characteristics, quantity, and quality of sleep. It allows the diagnosis of sleep-related disorders such as apnea syndrome, hypersomnia, narcolepsy, parasomnia, insomnia, etc. The clinical neurophysiologist is the specialist in all sleep disorders. Other specialties such as neurology only cover certain sleep pathologies, so it is best to always go to a clinical neurophysiologist, as it will give you a more complete and comprehensive view of the problem.

Intraoperative neurophysiological monitoring

It consists of the application of the previous techniques during those surgeries that present a high risk of producing a neurological lesion added to the previous pathology of the patient with the aim of preventing these lesions whenever possible. The techniques used are decided jointly between the neurophysiologist and the surgeon depending on the part of the nervous system that is at risk. It is used in surgery for tumors of the nervous system (of the brain, spinal cord or nerves), surgery for vascular aneurysms, some high-risk spinal surgeries such as scoliosis, etc. Function maps are also made in order to determine the location of the eloquent brain areas (language areas, motor area, sensitive area,...) to avoid injury during surgery. This is done using the electrocorticography technique.

Main diseases and disorders studied in clinical neurophysiology

• Epilepsy
• Epilepsy Surgery
• Muscle and motor plate
  • Myopathies
  • Motor plate diseases
  • Diseases with muscle hyperactivity
• Peripheral nerve
  • Mononeuropathies
  • Plexopathies
  • Polineuropathies
  • Sympathetic dystrophy reflects
• Radiculopathies
• Cervical myelopathy
• Degenerative diseases
  • Diseases of motor neuron
• Motion disorders
  • Tremor Studies
  • Mioclonia studies
  • Deep brain stimulation (Parkinson, headaches, etc.)
• Dream
  • Classification of sleep disorders
  • Disomnias
  • Parasomnias
• Vision
  • Retinopathy
• Hearing
  • Hipoacusia

In European countries in which Clinical Neurophysiology is recognized as an independent specialty, and its free circulation is recognized (Directive 98/63/CE, of September 3, 1998), such as Denmark, Spain, Finland, Ireland, Sweden, United Kingdom, Malta... at least 4 years of generic and specific training in accredited centers are required after reaching the Medical Degree.
In countries where Clinical Neurophysiology is a subspecialty, in order to carry out the specific training it is required to previously be a specialist in another neuroscience (for example Neurology, Psychiatry, Neurosurgery,...), as is the case in the United States, Germany, France, etc.
In most hospitals, Clinical Neurophysiology is found as a Central Service for complementary examinations, as diagnostic support and follow-up for various specialties: Neurology, Neurosurgery, Traumatology, Rehabilitation, Rheumatology, Pediatrics, Ophthalmology, Otorhinolaryngology (ORL), Internal Medicine, Intensive Medicine, Legal Medicine, Psychiatry, Pneumology, etc.

Clinical Neurophysiology in Spain

Clinical Neurophysiology is a medical specialty with a long tradition in Spain. The neurophysiological examinations that make up the specialty have been progressively implemented since 1937. The Clinical Neurophysiology Services (previously called Electroencephalography and Electroneurophysiology Services) were created in Spain in the 1960s. All the hospitals in the public network had Services of Neurophysiology, which basically performed electroencephalography and electromyography tests, and which progressively incorporated evoked potentials. The first Sleep Laboratory in Spain was created at the San Carlos Clinical Hospital in Madrid in 1973 and, from then on, polysomnographic studies were gradually implemented in the Clinical Neurophysiology Services. In 1968, the first residents in Clinical Neurophysiology began to be trained in a regulated manner at the University Clinical Hospitals.
Royal Decree 2015/1978 (BOE, 29-VIII-78) defines Clinical Neurophysiology as an independent medical specialty, regulating the training of specialists in Clinical Neurophysiology via MIR in all teaching hospitals. Since then, the Clinical Neurophysiology Services have been consolidating, both in public and private healthcare. The incessant scientific and technological progress has allowed a continuous development of the specialty. The demand for examinations has shown an exponential increase in the last 20 years, especially in electromyography, electroencephalography and polysomnography. In recent years, new techniques have been incorporated, such as intraoperative neurophysiological monitoring.

Clinical Neurophysiology in Europe

Since 1998, Clinical Neurophysiology is a specialty of free circulation in the European Union. The mutual recognition of the title is regulated by Directive 98/63/CE of the Commission of September 3, 1998. Official Gazette nº. L 253 of 09/15/1998 P. 0024 - 0026. The free circulation of specialists in Europe at the present time is restricted to countries that have the specialty carried out independently.