Sir Ganga Ram Hospital, New Delhi, India

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Department of Neurophysiology

[Front row sitting left to right: Inder Singh Baghari, Prem Singh Mehra, Dr. M. Gourie-Devi (Chairperson), Dr. Samhita Panda (Consultant), Dr. Kapil Sharma]

[Back row standing from left to right: Sonu, Prem Singh Adhikari, Vijay Sharma, Govind Singh Bisht, Dimple Kapur, Anjana Thakur, Arshiya Fatima, Dr. Hilal]


Neurophysiologic tests are essential to evaluate the function of central nervous system (brain, spinal cord, visual and auditory pathways) and peripheral nerves, neuromuscular junction and muscles. Abnormal tests provide valuable information which aid in diagnosis of a wide range of neurological disorders. The effect of treatment and progress of the illness can also be assessed by repeating the tests.

The diagnostic tests were first established at Sir Ganga Ram hospital in 1984 and during the next three decades, in keeping with the global developments, the department has acquired state of art equipments and has brought improvement in techniques to enhance the diagnostic accuracy.


Dr. M. Gourie-Devi is the Chairperson of Department of Neurophysiology. She is also i) Advisor to Indian Council of Medical Research (ICMR) for Neurology Research, ii) Emeritus Professor of Neurology, Institute of Human Behaviour and Allied Sciences, iii) Expert member of Council of Scientific and Industrial Research (CSIR), iv) World Health Organisation (WHO) and v) National Institute of Health (NIH), USA. Research Interests are: Motor Neuron Diseases (MND), Peripheral Neuropathy and Muscle Disorders.

Dr. Samhita Panda is a Consultant in Neurology and Vice-Chairperson of the departments of Clinical Neurophysiology and Sleep Medicine. She has been trained at AIIMS, Delhi and subsequently did a fellowship in Epilepsy and Sleep medicine. She has been trained in the pre-surgical evaluation of patients with refractory epilepsy. Research Interests are: Epilepsy, Sleep and Clinical Neurophysiology.

The department has a Senior Resident and DNB students from the department of Neurology are also posted as per their academic roster. The technical staff strength comprises six technicians presently. An active teaching and training programme for residents in neurology, visiting fellows and technicians has added vibrancy to the department.


i) Post graduate students of DNB in Neurology are posted to the department of Neurophysiology for two to three months on rotation, during which they receive intensive training in performance and interpretation of the diagnostic tests and their neurophysiologic basis. In addition, consultants in medicine and paediatrics or physiologists from different regions of the country opt to undergo training in the department on fellowship programme for a few months.

ii) The department of Neurophysiology initiated training programme in 1996 creating technical manpower. Every year, two trainees with science background are recruited for intensive training in all the neurophysiology diagnostic procedures through a ‘hands-on’ program strengthened by lectures by faculty and senior technicians of the department. During the course of 2 years the trainees are familiarized with the equipment, operation of the machines and learn to recognize and rectify commonly encountered artefacts. Preparation of the patient for the procedure, placement of electrodes, stimulation techniques and recording of the results are the essential components of the training programme. The candidates after successful completion of the course are employed as technicians in different hospitals and institutions in the country. Till date 17 technicians have completed training since 1993.


Presurgical evaluation of refractory epilepsy

The department of Clinical Neurophysiology in collaboration with the departments of Neurology, Neurosurgery, Neuroradiology, Nuclear medicine and Neuropsychology has recently started a comprehensive presurgical evaluation of refractory epilepsy. This new and innovative programme has been initiated for patients with refractory epilepsy who do not respond to 2 or more anti-epileptic drugs given in adequate doses for 2 years or more. This includes 16-channel Electroencephalography (EEG), neuropsychological evaluation, psychiatric evaluation, visual field charting, MRI of brain with protocol for hippocampal evaluation, video EEG monitoring, functional MRI of brain, interictal and Ictal SPECT of brain and FDG-PET scan of brain.

At the Refractory Epilepsy Board meetings, the results of various investigations along with clinical profile are presented and discussed in depth to assess the feasibility of surgical management. If the data is concordant on presurgical evaluation, surgery is considered. The patient and family members are communicated the decision at the board meeting itself and the patient and family members are encouraged to express their questions, doubts and concerns which are addressed by the board members. The surgically remediable lesions considered are mesial temporal lobe sclerosis, benign tumors such as ganglioglioma, DNET, oligodendroglioma , cortical dysplasia and vascular malformations. Other surgically treatable epilepsies that warrant consideration are Lennox Gastaut Syndrome and  Rasmussen’s encephalitis.

The tests done in the department include:
Preoperatively - Long term video EEG monitoring
Ictal SPECT in collaboration with the department of Nuclear Medicine.
Perioperatively- Electrocorticography (ECoG)
Postoperatively- EEGs at fixed intervals in the postoperative period


The Department of Neurophysiology offers diagnostic services for the comprehensive evaluation of diseases of central nervous system and peripheral nervous system.

The diagnostic tests carried out are listed below:-

  • Electroencephalography (EEG)
  • Short Term Video EEG monitoring (STVEEG)
  • Long Term Video EEG monitoring (LTVEEG)
  • Portable EEG Monitoring
  • Nerve Conduction Studies (NCS) (Sensory, motor, autonomic, blink reflex)
  • Electromyography (EMG)
  • Repetitive Nerve Stimulation (RNST)
  • Portable NCS, EMG, RNST
  • Evoked potential
    • Visual Evoked Potential (VEP)
    • Brainstem Auditory Evoked Potential (BAEP)
    • Somatosensory Evoked Potential (SSEP)
  • Electroretinography (ERG)
  • Presurgical evaluation for refractory epilepsy – LTVEEG, ictal SPECT (in coordination with department of Nuclear Medicine).
  • Intra-Operative Monitoring (IOM)


1. Electroencephalography (EEG)

The electrical activity of brain is recorded by this test. The record is analysed for abnormalities in brain rhythm.

EEG is done in the following conditions:

  • Epilepsy to confirm the diagnosis.
  • In spells of unconsciousness/ fainting - EEG is useful in differentiating these disorders from epilepsy.
  • Encephalitis (viral inflammation of brain e.g viral infections).
  • Dementia.
  • Stroke.
  • Brain tumour.

The EEG is useful for diagnosis, to decide about medication, in monitoring the response to treatment and in long term follow up to evaluate the course of the disease.

Details of Procedure

  • The test is painless.
  • The patient lies on the bed quietly.
  • Electrodes (small metal discs) are placed on the head.
  • During the test the patient may be asked to open and close the eyes on a few occasions, may be asked to breathe rapidly for few minutes. The patient is encouraged to relax with eyes closed and encouraged to sleep.
  • The time required for preparation and actual recording may take approximately 40-60 minutes.
  • There are no side effects.


  • Do not apply oil on the head.
  • Take a light meal, avoid fasting.
  • Take routine drugs.
  • Small children and uncooperative patients may be given sedative medicine.
  • This is an outpatient procedure. There is no need for admission to the hospital.

Recording of electroencephalograph on a digital system

2. Portable EEG

Portable EEG is done for seriously ill patients in the ICU and wards. Recording is done bedside using an ambulatory EEG machine. The report is promptly conveyed to the treating team. Portable EEG is useful in diagnosis of the following conditions, when patient cannot be shifted to the laboratory.

  • TEncephalitis
  • TStatus epilepticus• Metabolic Encephalopathy – hepatic, renal, drug overdose
  • THypoxic brain damage
  • TBrain Death

3. Nerve conduction studies (NCS)

  • TNerve conduction studies are used to evaluate the function of the nerves.
  • TThere are mainly two types of nerves - motor and sensory. The nerve conduction studies are specially designed to perform motor nerve conduction and sensory nerve conduction.

Nerve conduction studies is recommended for the following diseases:

  • Neuropathy in patients with diabetes mellitus.
  • Connective tissue diseases
  • Injury to the nerves
  • Carpal tunnel syndrome
  • Cervical/lumbar disc prolapse
  • Toxic effects of medications such as drugs taken for treatment of tuberculosis/ cancer
  • Guillain Barre Syndrome
  • Hereditary Neuropathy
  • Myasthenia.

Symptoms of nerve involvement

  • Tingling, numbness of hands/feet.
  • Burning sensation / pain in the hands and feet.
  • Decreased sensation in arms/legs.
  • Weakness /thinning of arms and legs.

Nerve conduction study in progress

Details of Procedure

  • Test usually takes 20-30minutes.
  • Metal disc plates (electrodes) are placed on the skin over nerves and muscles, mild electrical stimulation is given and the response is recorded.
  • Usually two nerves in upper limbs and two nerves in lower limbs are tested.
  • It may be necessary to test more nerves depending on the neurological disease.


  • Wear loose clothes as this will allow easy examination.
  • Fasting is not required.
  • For children who are uncooperative, sedation may be required.
  • There is no after effect following the test.
  • This is done as an outpatient procedure.

Technique of sensory conduction of right median nerve

4. Repetitive nerve stimulation (RNST)

Repetitive nerve stimulation test is a special type of nerve conduction study. Rather than a single electric shock, a brief series of shocks is applied to a motor nerve and responses are recorded from a muscle supplied by that nerve. The study is generally performed before and after brief exercise of the muscle. Serial response amplitudes are recorded. Repetitive nerve stimulation is useful for evaluating myasthenia gravis and other disorders of neuromuscular transmission.

5. Electromyography (EMG)

The EMG test is used to evaluate the status of the muscles, nerves, roots and anterior horn cells. A number of neurological disorders present with weakness or atrophy (thinning) of muscles. Some common disorders are:

  • Muscular dystrophy.
  • Myopathy.
  • Neuropathy.
  • Carpal tunnel syndrome.
  • Nerve injuries.
  • Cervical/lumbar radiculopathy.
  • Motor neuron diseases.

The EMG may be done either alone or in combination with nerve conduction studies (NCS) depending on the neurological disorder. Common symptoms of muscle involvement:

  • Difficulty in climbing stairs.
  • Difficulty in getting up from sitting/squatting position.
  • Difficulty in performing movements like buttoning, breaking chapatis, mixing food, combing hair.
  • Raising hands above the head.

Details of Procedure

  • A thin disposable EMG needle is inserted into the muscle to be examined. Depending on the type of disease one or more muscles may be required to be tested.
  • You may experience mild pain during the procedure.
  • There is no risk of transmitting the infection since disposable needles are used and they are destroyed after use.
  • You can have your regular food and medication on the day of the test.
  • You should wear loose clothes so that the test can be easily done.

6. Evoked potentials (EP)

Evoked potential (EP) is the electrical response recorded from brain, spinal cord or peripheral nerve evoked by various external stimuli, such as visual, auditory or somatosensory stimulation. The recording electrodes are placed over the scalp, neck or spine which vary depending on the type of stimulus modality to be tested. The evoked potential provides valuable information about the functional status and diseases affecting vision, hearing and sensory pathways.

6 a. Visual evoked potential (VEP)

VEP provides information regarding conduction in visual pathway from the retina to brain (occipital cortex).

VEP is recommended for following diseases associated with impairment of vision:

  • Multiple Sclerosis
  • Optic Neuritis
  • Tumours of the brain (pituitary tumours)
  • Head injuries
  • Drugs which may cause visual impairment
  • In children with mental retardation/ delayed development to assess visual status

Details of Procedure

  • The test is performed in dark room.
  • Each eye is tested separately.
  • The patient is asked to focus on a point on the monitor, which shows checkerboard pattern.
  • Small metals plates (electrodes) are applied to the head, which record the electrical potential.
  • The procedure usually take approximately 30 minutes.


  • Hair should be washed, dried, with no oil, gel, spray etc.
  • If the patient is using spectacles or contact lenses than he/she should wear them at the time of examination.
  • For children who are uncooperative sedation may be required.

Electroretinography (ERG)

ERG is performed to evaluate the visual function particularly in the patients suspected to have retinal diseases. It can be performed independently or with VEP.

6b. Brainstem Auditory Evoked Potential (BAER)

This test examines the integrity of auditory pathway through the brainstem. The sound enters the ear canal and stimulates auditory nerve. The electrical impulse travels from auditory nerve through the brainstem to auditory cortex. During testing, the patient hears the repetitive click sound through the earphone.

BAER is recommended for following diseases:

  • Hearing problem
  • Dizziness/ Vertigo
  • Multiple Sclerosis
  • Tumours of the Brainstem
  • Head Injuries
  • Delayed development in children
  • Jaundice in children.

Details of Procedure

  • The procedure is carried in a sound proof room.
  • The stimulus is provided using headphone in one ear followed by second ear.
  • The electrical response is recorded by small metal plates (electrodes).
  • The test is not painful.


  • Hair should be washed, dried, with no oil, gel, spray etc.
  • For children who are uncooperative sedation may be required.
  • The procedure usually take approximately 30 minutes.

Brainstem auditory evoked potential study in progess with graph

6c. Somatosensory evoked potential (SSEP)

This test examines the sensory system from the peripheral nerve to the sensory cortex of brain. Weak electrical stimuli are applied to the peripheral nerve, for example median or ulnar nerve for upper extremity study and tibial nerve for lower extremity study.

SSEP is recommended for following diseases:

  • Numbness/ weakness of arm or leg.
  • Diseases of the spinal cord.
  • Multiple Sclerosis.

Details of Procedure

  • The electrical stimulation is applied to nerve in the arm or the leg.
  • The response is recorded from the neck and the head by electrodes placed over the surface.
  • Mild pain is experienced when electrical stimulation is applied.


  • Should wear loose clothes, which will allow easy examination.
  • Fasting not required.
  • For children who are uncooperative sedation may be required.
  • There is no after effect following the test.
  • This is done as an outpatient procedure.

 7. Video-EEG / Long term recording

Video EEG monitoring is undertaken for the patients who have recurrent episodes of loss of consciousness, altered sensorium and seizures. The indications for video EEG are-

  • Diagnosis of paroxysmal events including abnormal movements
  • Diagnosis of non-epileptic behavioural events
  • Diagnosis of seizure type/s
  • Rule out combination of true and pseudoseizures
  • As part of presurgical evaluation for epilepsy surgery

The duration of VEEG depends on the clinical disorders, seizure frequency and indication for the video EEG. This can range from 1-3 hours in patients with frequent events (hourly) to 4-5 days in patients with infrequent events and evaluation prior to surgery. One attendant should accompany the patient during the procedure. The EEG along with the patient’s video is recorded simultaneously to evaluate the nature of events.

During events, the clinical onset and semiology of the event is noted. The EEG changes during these events are also noted. The semiology of the clinical events is correlated with the EEG abnormalities. Using this study, the ictal onset zone can be delineated. This is an important component of the presurgical evaluation for medically refractory epilepsy.

Video EEG facilities and expertise is available is only few institutions in the country. The hospital has a well-established video-EEG set-up and more than 400 such procedures have been done.

8. Intraoperative monitoring (IOM)

This is performed in the operation theatre during surgery. This special monitoring is in demand during neurosurgical and orthopaedic procedures to avoid inadvertent damage to the nerves and neurological tissue in the vicinity. Intraoperative neurophysiologic monitoring minimizes neurological morbidity from operative manipulations. It identifies changes in brain, spinal cord, and peripheral nerve function prior to irreversible damage and also localizes anatomical structures, such as peripheral nerves and sensorimotor cortex. Evoked potential monitoring including SSEP, BAER, motor evoked potentials (MEP), and VEP as well as EMG is used during operative cases. IOM helps to differentiate the nerves fibers from connective tissue during surgery particularly in region of cerebellopontine angle and brain stem. The use of this technique helps to prevent complications. Similarly, SSEP is used for monitoring the preservation of spinal cord during scoliosis surgery.Intraoperative scalp EEG can be used to monitor cerebral function during carotid or other vascular surgery. Electrocorticography using subdural electrodes directly over the pial surface can help determine resection margins for epilepsy surgery, and mapping cortical function.