Director(Neuro Medicine)

Chandan Institute of Neuro Sciences

Dr. Pankaj Kumar Popli

MD (Medicine), KGMU, Lucknow
DM (Neurology), SGPGI, Lucknow

Director(Neuro Surgery)

Chandan Institute of Neuro Sciences

Dr. Mohd. Iqbal

MS (General Surgery)
M Ch (Neurosurgery)
PDF (Spine surgery) SGPGIMS, Lucknow.
PDF (Skull base surgery) SGPGIMS, Lucknow.
Fellow Neurointervention , FMU, Japan.
Fellow Neuro-oncology, FMU, Japan.
Fellow Neuro-endoscopy, NSCB Medical College, Jabalpur

Neurology at Chandan Hospital is a branch of medicine dealing with disorders of the nervous system. Neurology deals with the diagnosis and treatment of all categories of conditions and disease involving the central and peripheral nervous systems (and their subdivisions, the autonomic and somatic nervous systems), including their coverings, blood vessels, and all effector tissue, such as muscle.

Neurology include imaging studies such as computed axial tomography (CAT) scans, magnetic resonance imaging (MRI), and ultrasound of major blood vessels of the head and neck. Neurophysiologic studies, including electroencephalography (EEG), needle electromyography(EMG), nerve conduction studies (NCSs) and evoked potentials are also commonly ordered. Neurologists frequently perform lumbar punctures to assess characteristics of a patient's cerebrospinal fluid.

Some of the commonly encountered conditions treated by neurologists include headaches, radiculopathy, neuropathy, stroke, dementia, seizures and epilepsy, Alzheimer's disease, attention deficit/hyperactivity disorder, Parkinson's disease, Tourette's syndrome, multiple sclerosis, head trauma, sleep disorders, neuromuscular diseases, and various infections and tumors of the nervous system.

Neurosurgery, or neurological surgery is the medical specialty concerned with the prevention, diagnosis, surgical treatment, and rehabilitation of disorders which affect any portion of the nervous system including the brain, spinal cord, peripheral nerves, and cerebrovascular system.

General neurosurgery involves most neurosurgical conditions including neuro-trauma and other neuro-emergencies such as intracranial hemorrhage.

  • Vascular neurosurgery
  • Interventional neuroradiology / Endovascular surgical neuroradiology
  • Stereotactic neurosurgery, functional neurosurgery, and epilepsy surgery (the latter includes partial or total corpus callosotomy - severing part or all of the corpus callosum to stop or lessen seizure spread and activity, and the surgical removal of functional, physiological and/or anatomical pieces or divisions of the brain, called epileptic foci, that are operable and that are causing seizures, and also the more radical and very, very rare partial or total lobectomy, or even hemispherectomy - the removal of part or all of one of the lobes, or one of the cerebral hemispheres of the brain; those two procedures, when possible, are also very, very rarely used in oncological neurosurgery or to treat very severe neurological trauma, such as stab or gunshot wounds to the brain)
  • Oncological neurosurgery also called neurosurgical oncology; includes pediatric oncological neurosurgery; treatment of benign and malignant central and peripheral nervous system cancers and pre-cancerous lesions in adults and children (including, among others, glioblastoma multiforme and other gliomas, brain stem cancer, astrocytoma, pontine glioma, medulloblastoma, spinal cancer, tumors of the meninges and intracranial spaces, secondary metastases to the brain, spine, and nerves, and peripheral nervous system tumors)
  • Skull base surgery
  • Spinal neurosurgery
  • Peripheral nerve surgery
  • Pediatric neurosurgery (for cancer, seizures, bleeding, stroke, cognitive disorders or congenital neurological disorders)

Neuroradiology methods are used in modern neurosurgery diagnosis and treatment. They include computer-assisted imaging computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), magnetoencephalography (MEG), and stereotactic radiosurgery. Some neurosurgery procedures involve the use of intra-operative MRI and functional MRI.

In conventional open surgery the neurosurgeon opens the skull, creating a large opening to access the brain. Techniques involving smaller openings with the aid of microscopes and endoscopes are now being used as well. Methods that utilize small craniotomies in conjunction with high-clarity microscopic visualization of neural tissue offer excellent results. However, the open methods are still traditionally used in trauma or emergency situations.

Microsurgery is utilized in many aspects of neurological surgery. Microvascular techniques are used in EC-IC bypass surgery and in restoration carotid endarterectomy. The clipping of an aneurysm is performed under microscopic vision. Minimally invasive spine surgery utilizes microscopes or endoscopes. Procedures such as microdiscectomy, laminectomy, and artificial disc replacement rely on microsurgery.

Minimally invasive endoscopic surgery is commonly utilized by neurosurgeons when appropriate. Techniques such as endoscopic endonasal surgery are used in pituitary tumors, craniopharyngiomas, chordomas, and the repair of cerebrospinal fluid leaks. Ventricular endoscopy is used in the treatment of intraventricular bleeds, hydrocephalus, colloid cyst and neurocysticercosis. Endonasal endoscopy is at times carried out with neurosurgeons and ENT surgeons working together as a team.

Repair of craniofacial disorders and disturbance of cerebrospinal fluid circulation is done by neurosurgeons who also occasionally team up with maxillofacial and plastic surgeons. Cranioplasty for craniosynostosis is performed by pediatric neurosurgeons with or without plastic surgeons.

Neurosurgeons are involved in stereotactic radiosurgery along with radiation oncologists in tumor and AVM treatment. Radiosurgical methods such as Gamma Knife, Cyberknife and Novalis Radiosurgery are used as well.

A common procedure performed in neurosurgery is the placement of ventriculoperitoneal shunts (commonly referred to as "VP shunts"). In pediatric practice, VP shunts are commonly placed in cases of congenital hydrocephalus. The most common indication for this procedure in adults is normal-pressure hydrocephalus (NPH).

Neurosurgery of the spine covers the cervical, thoracic and lumbar spine. Some indications for spine surgery include spinal cord compression resulting from trauma, arthritis of the spinal discs, or spondylosis. In cervical cord compression, patients may have difficulty with gait, balance issues, and/or numbness and tingling in the hands or feet. Spondylosis is the condition of spinal disc degeneration and arthritis that may compress the spinal canal. This condition can often result in bone spurring and disc herniation. Power drills and special instruments are often used to correct any compression problems of the spinal canal. Disc herniations of spinal vertebral discs are removed with special rongeurs. This procedure is known as a discectomy. Generally once a disc is removed it is replaced by an implant which will create a bony fusion between vertebral bodies above and below. Instead, a mobile disc could be implanted into the disc space to maintain mobility. This is commonly used in cervical disc surgery. At times instead of disc removal a Laser discectomy could be used to decompress a nerve root. This method is mainly used for lumbar discs. Laminectomy is the removal of the lamina portion of the vertebrae of the spine in order to make room for the compressed nerve tissue.

Radiology-assisted spine surgery uses minimally-invasive procedures. They include the techniques of vertebroplasty and kyphoplasty, in which certain types of spinal fractures are managed. Potentially unstable spines require spine fusions. At present these procedures include complex instrumentation. Spine fusions maybe performed as open surgery or as minimally invasive surgery. Anterior cervical diskectomy and fusion is a common surgery that is performed for disc disease of the cervical spine.

Conditions treated by neurosurgeons include
  • Meningitis and other central nervous system infections including abscesses
  • Spinal disc herniation
  • Cervical spinal stenosis and Lumbar spinal stenosis
  • Hydrocephalus
  • Head trauma (brain hemorrhages, skull fractures, etc.)
  • Spinal cord trauma
  • Traumatic injuries of peripheral nerves
  • Tumors of the spine, spinal cord and peripheral nerves
  • Intracerebral hemorrhage, such as subarachnoid hemorrhage, interdepartmental, and intracellular hemorrhages
  • Some forms of drug-resistant epilepsy
  • Some forms of movement disorders (advanced Parkinson's disease, chorea) – this involves the use of specially developed minimally invasive stereotactictechniques (functional, stereotactic neurosurgery) such as ablative surgery and deep brain stimulation surgery
  • Intractable pain of cancer or trauma patients and cranial/peripheral nerve pain
  • Some forms of intractable psychiatric disorders
  • Vascular malformations (i.e., arteriovenous malformations, venous angiomas, cavernous angiomas, capillary telangectasias) of the brain and spinal cord
  • Moyamoya disease

Electromyography-

Electromyography (EMG) at Chandan Hospital is an electro-diagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect medical abnormalities, activation level, or recruitment order, or to analyze the biomechanics of patients.

Medical Uses:

EMG testing has a variety of clinical and biomedical applications. EMG is used as a diagnostics tool for identifying neuromuscular diseases and disorders of motor control.

Except in the case of some purely primary myopathic conditions EMG is usually performed with another electrodiagnostic medicine test that measures the conducting function of nerves. This is called a nerve conduction studies (NCS). Needle EMG and NCSs are typically indicated when there is pain in the limbs, weakness from spinal nerve compression, or concern about some other neurologic injury or disorder. Spinal nerve injury does not cause neck, mid back pain or low back pain, and for this reason, evidence has not shown EMG or NCS to be helpful in diagnosing causes of axial lumbar pain, thoracic pain, or cervical spine pain. Needle EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.

Maximal voluntary contraction:

One basic function of EMG is to see how well a muscle can be activated. The most common way that can be determined is by performing a maximal voluntary contraction (MVC) of the muscle that is being tested.

Muscle force, which is measured mechanically, typically correlates highly with measures of EMG activation of muscle. Most commonly this is assessed with surface electrodes, but it should be recognized that these typically only record from muscle fibers in close approximation to the surface.

Chandan Hospital has facility for Nerve conduction velocity which studies the nerve conduction. It is the speed at which an electrochemical impulse propagates down a neural pathway.

Conduction velocities are affected by a wide array of factors, including age, sex, and various medical conditions. Studies allow for better diagnoses of various neuropathies, especially demyelinating conditions as these conditions result in reduced or non-existent conduction velocities.

Medical conditions-

Amyotrophic lateral sclerosis (ALS) : Amyotrophic Lateral Sclerosis (ALS) is a progressive and inevitably fatal neurodegenerative disease affecting the motor neurons. Because ALS shares many symptoms with other neurodegenerative diseases, it can be difficult to diagnose properly. The best method of establishing a confident diagnosis is via electrodiagnostic evaluation. To be specific, motor nerve conduction studies of the Median, Ulnar, and peroneal muscles should be performed, as well as sensory nerve conduction studies of the Ulnar and Sural nerves.

In patients with ALS, it has been shown that distal motor latencies and slowing of conduction velocity worsened as the severity of their muscle weakness increased. Both symptoms are consistent with the axonal degeneration occurring in ALS patients.

Carpal tunnel syndrome : Carpal tunnel syndrome (CTS) is a form of nerve compression syndrome caused by the compression of the median nerve at the wrist. Typical symptoms include numbness, tingling, burning pains, or weakness in the hand. CTS is another condition for which electrodiagnostic testing is valuable. However, before subjecting a patient to nerve conduction studies, both Tinel's test and Phalen's test should be performed. If both results are negative, it is very unlikely that the patient has CTS, and further testing is unnecessary.

Carpal tunnel syndrome presents in each individual to different extents. Measurements of nerve conduction velocity are critical to determining the degree of severity. These levels of severity are categorized as:

  • Mild CTS: Prolonged sensory latencies, very slight decrease in conduction velocity. No suspected axonal degeneration.
  • Moderate CTS: Abnormal sensory conduction velocities and reduced motor conduction velocities. No suspected axonal degeneration.
  • Severe CTS: Absence of sensory responses and prolonged motor latencies (reduced motor conduction velocities).
  • Extreme CTS: Absence of both sensory and motor responses.

One common electrodiagnostic measurement includes the difference between sensory nerve conduction velocities in the pinkie finger and index finger. In most instances of CTS, symptoms will not present until this difference is greater than 8 m/s.

Guillain-Barré syndrome : Guillain-Barré syndrome (GBS) is a peripheral neuropathy involving the degeneration of myelin sheathing and/or nerves that innervate the head, body, and limbs. This degeneration is due to an autoimmune response typically initiated by various infections.

Two primary classifications exist: demyelinating (Schwann cell damage) and axonal (direct nerve fiber damage). Each of these then branches into additional sub-classifications depending on the exact manifestation. In all cases, however, the condition results in weakness or paralysis of limbs, the potentially fatal paralysis of respiratory muscles, or a combination of these effects.

The disease can progress very rapidly once symptoms present (severe damage can occur within as little as a day). Because electrodiagnosis is one of the fastest and most direct methods of determining the presence of the illness and its proper classification, nerve conduction studies are extremely important. Without proper electrodiagnostic assessment, GBS is commonly misdiagnosed as Polio, West Nile virus, Tick paralysis, various Toxic neuropathies, CIDP, Transverse myelitis, or Hysterical paralysis. Two sets of nerve conduction studies should allow for proper diagnosis of Guillain-Barré syndrome. It is recommended that these be performed within the first 2 weeks of symptom presentation and again sometime between 3 and 8 weeks.

Electrodiagnostic findings that may implicate GBS include:

  • Complete conduction blocks
  • Abnormal or absent F waves
  • Attenuated compound muscle action potential amplitudes
  • Prolonged motor neuron latencies
  • Severely slowed conduction velocities (sometimes below 20 m/s)

Lambert-Eaton myasthenic syndrome : Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease in which auto-antibodies are directed against voltage-gated calcium channels at presynaptic nerve terminals. Here, the antibodies inhibit the release of neurotransmitters, resulting in muscle weakness and autonomic dysfunctions.

Nerve conduction studies performed on the Ulnar motor and sensory, Median motor and sensory, Tibial motor, and Peroneal motor nerves in patients with LEMS have shown that the conduction velocity across these nerves is actually normal. However, the amplitudes of the compound motor action potentials may be reduced by up to 55%, and the duration of these action potentials decreased by up to 47%.

Peripheral diabetic neuropathy : At least half the population with diabetes mellitus is also affected with diabetic neuropathy, causing numbness and weakness in the peripheral limbs. Studies have shown that the Rho/Rho-kinase signaling pathway is more active in individuals with diabetes and that this signaling activity occurs mainly in the nodes of Ranvier and Schmidt-Lanterman incisures. Therefore, over-activity of the Rho/Rho-kinase signaling pathway may inhibit nerve conduction.

Motor nerve conduction velocity studies revealed that conductance in diabetic rats was about 30% lower than that of the non-diabetic control group. In addition, activity along the Schmidt-Lanterman incisures was non-continuous and non-linear in the diabetic group, but linear and continuous in the control. These deficiencies were eliminated after the administration of Fasudil to the diabetic group, implying that it may be a potential treatment.

Electroencephalography (EEG) at Chandan Hospital is an electrophysiological monitoring method to record electrical activity of the brain. It is typically noninvasive, with the electrodes placed along the scalp, although invasive electrodes are sometimes used such as in electrocorticography. EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain. In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a period of time, as recorded from multiple electrodes placed on the scalp. Diagnostic applications generally focus either on event-related potentials or on the spectral content of EEG. The former investigates potential fluctuations time locked to an event like stimulus onset or button press. The latter analyses the type of neural oscillations (popularly called "brain waves") that can be observed in EEG signals in the frequency domain.

EEG is most often used to diagnose epilepsy, which causes abnormalities in EEG readings. It is also used to diagnose sleep disorders, depth of anesthesia, coma, encephalopathies, and brain death. EEG used to be a first-line method of diagnosis for tumors, stroke and other focal brain disorders, but this use has decreased with the advent of high-resolution anatomical imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). Despite limited spatial resolution, EEG continues to be a valuable tool for research and diagnosis. It is one of the few mobile techniques available and offers millisecond-range temporal resolution which is not possible with CT, PET or MRI.

ADVANTAGES:

Several other methods to study brain function exist, including functional magnetic resonance imaging (fMRI), positron emission tomography, magnetoencephalography(MEG), nuclear magnetic resonance spectroscopy, electrocorticography, single-photon emission computed tomography, near-infrared spectroscopy (NIRS), and event-related optical signal (EROS). Despite the relatively poor spatial sensitivity of EEG, it possesses multiple advantages over some of these techniques:

  • Complete conduction blocks
  • Abnormal or absent F waves
  • Attenuated compound muscle action potential amplitudes
  • Prolonged motor neuron latencies
  • Severely slowed conduction velocities (sometimes below 20 m/s)
  • EEG prevents limited availability of technologists to provide immediate care in high traffic hospitals.
  • EEG sensors can be used in more places than fMRI, SPECT, PET, MRS, or MEG, as these techniques require bulky and immobile equipment. For example, MEG requires equipment consisting of liquid helium-cooled detectors that can be used only in magnetically shielded rooms, altogether costing upwards of several million dollars; and fMRI requires the use of a 1-ton magnet in, again, a shielded room.
  • EEG has very high temporal resolution, on the order of milliseconds rather than seconds. EEG is commonly recorded at sampling rates between 250 and 2000 Hz in clinical and research settings, but modern EEG data collection systems are capable of recording at sampling rates above 20,000 Hz if desired. MEG and EROS are the only other noninvasive cognitive neuroscience techniques that acquire data at this level of temporal resolution.
  • EEG is relatively tolerant of subject movement, unlike most other neuroimaging techniques. There even exist methods for minimizing, and even eliminating movement artifacts in EEG data
  • EEG is silent, which allows for better study of the responses to auditory stimuli.
  • EEG does not aggravate claustrophobia, unlike fMRI, PET, MRS, SPECT, and sometimes MEG
  • EEG does not involve exposure to high-intensity (>1 tesla) magnetic fields, as in some of the other techniques, especially MRI and MRS. These can cause a variety of undesirable issues with the data, and also prohibit use of these techniques with participants that have metal implants in their body, such as metal-containing pacemakers
  • EEG does not involve exposure to radioligands, unlike positron emission tomography.
  • ERP studies can be conducted with relatively simple paradigms, compared with IE block-design fMRI studies.
  • Extremely uninvasive, unlike Electrocorticography, which actually requires electrodes to be placed on the surface of the brain.
  • EEG also has some characteristics that compare favorably with behavioral testing.
  • EEG can detect covert processing (i.e., processing that does not require a response)
  • EEG can be used in subjects who are incapable of making a motor response
  • Some ERP components can be detected even when the subject is not attending to the stimuli
  • Unlike other means of studying reaction time, ERPs can elucidate stages of processing (rather than just the final end result)
  • EEG is a powerful tool for tracking brain changes during different phases of life. EEG sleep analysis can indicate significant aspects of the timing of brain development, including evaluating adolescent brain maturation.
  • EEG there is a better understanding of what signal is measured as compared to other research techniques, i.e. the BOLD response in MRI.

Electromyography(EMG)

Electromyography (EMG) at Chandan Hospital is an electro-diagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect medical abnormalities, activation level, or recruitment order, or to analyze the biomechanics of patients.

Medical uses :

EMG testing has a variety of clinical and biomedical applications. EMG is used as a diagnostics tool for identifying neuromuscular diseasesand disorders of motor control.

Except in the case of some purely primary myopathic conditions EMG is usually performed with another electrodiagnostic medicine test that measures the conducting function of nerves. This is called a nerve conduction studies (NCS). Needle EMG and NCSs are typically indicated when there is pain in the limbs, weakness from spinal nerve compression, or concern about some other neurologic injury or disorder. Spinal nerve injury does not cause neck, mid back pain or low back pain, and for this reason, evidence has not shown EMG or NCS to be helpful in diagnosing causes of axial lumbar pain, thoracic pain, or cervical spine pain. Needle EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.

Technique :

Skin preparation and risks :

The first step before insertion of the needle electrode is skin preparation. This typically involves simply cleaning the skin with an alcohol pad.

The actual placement of the needle electrode can be difficult and depends on a number of factors, such as specific muscle selection and the size of that muscle. Proper needle EMG placement is very important for accurate representation of the muscle of interest, although EMG is more effective on superficial muscles as it is unable to bypass the action potentials of superficial muscles and detect deeper muscles. Also, the more body fat an individual has, the weaker the EMG signal. When placing the EMG sensor, the ideal location is at the belly of the muscle: the longitudinal midline. The belly of the muscle can also be thought of as in-between the motor point (middle) of the muscle and the tendonus insertion point.

Surface and intramuscular EMG recording electrodes :

There are two kinds of EMG: surface EMG and intramuscular EMG.

Surface EMG

Surface EMG assesses muscle function by recording muscle activity from the surface above the muscle on the skin. Surface electrodes are able to provide only a limited assessment of the muscle activity. Surface EMG can be recorded by a pair of electrodes or by a more complex array of multiple electrodes. More than one electrode is needed because EMG recordings display the potential difference (voltage difference) between two separate electrodes. Limitations of this approach are the fact that surface electrode recordings are restricted to superficial muscles, are influenced by the depth of the subcutaneous tissue at the site of the recording which can be highly variable depending of the weight of a patient, and cannot reliably discriminate between the discharges of adjacent muscles.

Intramuscular EMG

Intramuscular EMG can be performed using a variety of different types of recording electrodes. The simplest approach is a monopolar needle electrode. This can be a fine wire inserted into a muscle with a surface electrode as a reference; or two fine wires inserted into muscle referenced to each other. Most commonly fine wire recordings are for research or kinesiology studies. Diagnostic monopolar EMG electrodes are typically insulated and stiff enough to penetrate skin, with only the tip exposed using a surface electrode for reference. Needles for injecting therapeutic botulinum toxin or phenol are typically monopolar electrodes that use a surface reference, in this case, however, the metal shaft of a hypodermic needle, insulated so that only the tip is exposed, is used both to record signals and to inject. Slightly more complex in design is the concentric needle electrode. These needles have a fine wire, embedded in a layer of insulation that fills the barrel of a hypodermic needle, that has an exposed shaft, and the shaft serves as the reference electrode. The exposed tip of the fine wire serves as the active electrode. As a result of this configuration, signals tend to be smaller when recorded from a concentric electrode than when recorded from a monopolar electrode and they are more resistant to electrical artifacts from tissue and measurements tend to be somewhat more reliable. However, because the shaft is exposed throughout its length, superficial muscle activity can contaminate the recording of deeper muscles. Single fiber EMG needle electrodes are designed to have very tiny recording areas, and allow for the discharges of individual muscle fibers to be discriminated.

To perform intramuscular EMG, typically either a monopolar or concentric needle electrode is inserted through the skin into the muscle tissue. The needle is then moved to multiple spots within a relaxed muscle to evaluate both insertional activity and resting activity in the muscle. Normal muscles exhibit a brief burst of muscle fiber activation when stimulated by needle movement, but this rarely lasts more than 100ms. The two most common pathologic types of resting activity in muscle are fasciculation and fibrillation potentials. A fasciculation potential is an involuntary activation of a motor unit within the muscle, sometimes visible with the naked eye as a muscle twitch or by surface electrodes. Fibrillations, however, are only detected by needle EMG, and represent the isolated activation of individual muscle fibers, usually as the result of nerve or muscle disease. Often, fibrillations are triggered by needle movement (insertional activity) and persist for several seconds or more after the movement ceases.

After assessing resting and insertional activity, the electromyographer assess the activity of muscle during voluntary contraction. The shape, size, and frequency of the resulting electrical signals are judged. Then the electrode is retracted a few millimetres, and again the activity is analyzed. This is repeated, sometimes until data on 10–20 motor units have been collected in order to draw conclusions about motor unit function. Each electrode track gives only a very local picture of the activity of the whole muscle. Because skeletal muscles differ in the inner structure, the electrode has to be placed at various locations to obtain an accurate study.

Single fiber electromyography assesses the delay between the contractions of individual muscle fibers within a motor unit and is a sensitive test for dysfunction of the neuromuscular junction caused by drugs, poisons, or diseases such as myasthenia gravis. The technique is complicated and typically only performed by individuals with special advanced training.

Maximal voluntary contraction:

One basic function of EMG is to see how well a muscle can be activated. The most common way that can be determined is by performing a maximal voluntary contraction (MVC) of the muscle that is being tested.

Muscle force, which is measured mechanically, typically correlates highly with measures of EMG activation of muscle. Most commonly this is assessed with surface electrodes, but it should be recognized that these typically only record from muscle fibers in close approximation to the surface.

Auditory Brainstem Response

The brainstem evoked response audiometry (BERA) is an objective neurophysiological method for the evaluation of the hearing threshold and diagnosing retrocochlear lesions. The aim of the study is to investigate the hearing level in children with suspected hearing loss or pathological speech development.The auditory brainstem response (ABR) is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp. The measured recording is a series of six to seven vertex positive waves of which I through V are evaluated. The ABR is considered an exogenous response because it is dependent upon external factors.

Procedure :

The stimulus either in the form of click or tone pip is transmitted to the ear via a transducer placed in the insert ear phone or head phone. The wave froms of impulses generated at the level of brain stem are recorded by the placement of electrodes over the scalp.

Electrode placement: Since the electrodes should be placed over the head, the hair must be oil free. The patient should be instructed to have shampoo bath before coming for investigation. The standard electrode configuration for BERA involves placing a non inverting electrode over the vertex of the head, and inverting electrodes placed over the ear lobe or mastoid prominence. One more earthing electrode is placed over the forehead. This earthing electrode is important for proper functioning of preamplifier.

The auditory structures that generate the auditory brainstem response are believed to be as follows :
  • Wave I through III – generated by the auditory branch of cranial nerve VIII and lower
  • Wave IV and V – generated by the upper brainstem
  • More in depth location – wave I originates from the dendrites of the auditory nerve fibers, wave II from the cochlear nucleus, III showing activity in the superior olivary complex, and wave IV–V associated with the lateral lemniscus.
  • There are two different types of auditory evoked potential tests. These tests are being used as an adjunct to routine diagnostic testing. The two types of auditory evoked potential tests are: 1. Auditory brain stem response and 2. Auditory cortical response.
  • Auditory cortical response: Records the impulses generated by brain in response to tone stimuli. It is recorded using cortical response audiometry (CERA). CERA is very useful for threshold estimation of hearing, whereas BERA is highly useful for objective threshold estimation of hearing as well as differential diagnostic purposes. These responses are more generalised and originate from the brain cortex occurring between 50 - 300 milliseconds after the onset of stimulation. Since these responses are generally elicited with a tone burst lasting approximately for about 200 milliseconds, its responses are highly frequency specific. This is in contrast to BERA because brain stem responses are evoked by click stimuli and are not frequency specific. Interpretation of CERA is easy and straightforward. Threshold is defined as the minimum stimulus level that gives a consistent and identifiable response. The patient must be lying still during the recording process. This test is hence unsuitable for young children who may not co-operate
Differences between BERA and CERA :
BERA CERA
Recording is made from brain stem potentials Recording is made from cortical potentials
Click stimulus is used Tone stimulus is used
Responses are not frequnency specific Responses are frequency specific
Can be performed in awake and restless patients The patient must lie still through out the process
Responses begin after 1 - 10 milliseconds after stimuli Response begins after 50 - 300 milliseconds after stimulation
Suitable for even young children Unsuitable for children

Use :

  • 1. It is an effective screening tool for evaluating cases of deafness due to retrocochlear pathology i.e. (Acoustic schwannoma). An abnormal BERA is an indication for MRI scan.
  • 2. Used in screening newborns for deafness
  • 3. Used for intraoperative monitoring of central and peripheral nervous system
  • 4. Monitoting patients in intensive care units
  • 5. Diagnosing suspected demyelinated disorders
BERA findings suggestive of retrocochlear pathology :
  • 1. Latency differences between interaural wave 5 (prolonged in cases of retrocochlear pathology)
  • 2. Waves I - V interaural latency differences - prolonged
  • 3. Absolute latency of wave V - prolonged
  • 4. Absence of brain stem response in the affected ear

BERA has 90% sensitivity and 80% specificity in identifying cases of acoustic schwannoma. The sensitivity increases in proportion to the size of the tumor.

Criteria for screening newborn babies using BERA:
  • 1. Parental concern about hearing levels in their child
  • 2. Family history of hearing loss
  • 3. Pre and post natal infections
  • 4. Low birth weight babies
  • 5. Hyperbilirubinemia
  • 6. Cranio facial deformities
  • 7. Head injury
  • 8. Persistent otitis media
  • 9. Exposure to ototoxic drugs