Vertigo testing by Computerized Electronystagmography (CENG)

Equipment and set up for CENG testing

The inner ear is the main organ which maintains the body’s balance.

It is situated deep within the skull (within th temporal bone).

Any organ of the human body can nowadays be visualised by radio imaging (C.T. scans for bony abnormalities and M.R. Scan or Sonography for soft tissues, basically without “intervention” entry into the body).

Any organ of the human body canalso have its function assessed by measuring the electrical impulses emitted by electrodes placed on the surface of the body. To give an example, an electro cardiogram records electrical impulses from the heart from the surface of the body by means of electrodes. An X-Ray of the chest shows heart size to be normal but the ECG may be significantly normal.

Similarly, the CENG is a test of the function of the inner ear. The CENG test is the gold-standard for diagnosis of balance disorders. It is a recording of the electrical activity of the balance organ and its connections with the balance centers at the base of the brain, brain stem and cerebellum, all of which contribute to the maintenance of the body’s balance.

2 groups of tests are available – The Oculomotor tests and the Vestibular tests

Tests employed for balance disorders

Patient wired up for Computerised Electronystagmography

Oculomotor Tests (Tests integrity of nerve connections between eyes and inner ear balance organ)

• Spontaneous nystagmus test

Whenever there is disease anywhere in the balance organs or their connections with the central nervous system, eyes or cervical spine, triangular beats – quick short beat and long beat known as nystagmus are obtained. These can be recorded on CENG even with eyes closed.

• Calibration and Saccade test – To and fro movement of eyes on following 2 fixed points

• Gaze nystagmus test – Records abnormal eye movement on gazing left, right, up or down.

• Optokinetic tracking test – Recordings of eye movement on following a moving target.

An Optokinetic stimulator. Patient’s gaze follows moving LEDs and recordings are obtained.

Recording of Saccades                                                     Recording of Optokinetic target tracking

Vestibular tests

  1. Positional tests determine whether dizziness originates from different positions of the head.

Positional testing is to detect positional nystagmus in cases of vertigo which comes on with change of  position of head and body in specific positions (Hallpike positions). If there is positional nystagmus, to determine if it is due to the ear (usually BPPV), brain (central positional nystagmus), or neck (cervicogenic vertigo).

Caloric test

Whether spontaneous nystagmus is present or not, recordings are also obtained by stimulating the inner ear balance organs. The patient lies on a couch. Water at 7 degrees above and 7 degrees below body temperature (30 and 44 degrees centigrade) is irrigated into the ear on one side at a time, for 40 seconds  The water stimulates the inner ear fluids setting up convection currents.

Right ear stimulus and Left ear stimulus give nystagmus responses in opposite directions. The recordings are analysed by a computer and nystagmus parameters of velocity, frequency and amplitude are analysed and graphs obtained.

This is the most important test for analysis of the function of the inner ear and its connections.

 

Recordings of the Caloric test

Recording of right and left ear caloric responses for frequency calculation

BALANCE  DISORDERS  include               

 Vertigo – a sensation of rotation of self or surroundings, often with nausea, vomiting and sweating, a sensation of swaying of self. A deafness &/or tinnitus (noise in the ear may be present.

Dizziness – Swimming sensation or some movement in the head

Giddiness – Swaying sensation on standing or sitting

Imbalance on sitting /walking and likelihood of falling

Dysequilibrium, Unsteadiness

Anatomy and Physiology of the ear
 Most balance disorders are due to a malfunction of one or both labyrinths – the organs in the internal ear which are the chief organs that maintain the body’s balance. Being in the ear, the first examination of a patient with a balance disorder should be performed by an ENT specialist skilled in clinical examination and performing investigations for balance disorders – recording the function of the inner ears by CENG  (Computerised Electro Nystagmo Graphy with Spontaneous nystagmus and with Caloric testing.

(VENG is valid only if done with Caloric testing and recording of Spontaneous nystagmus).

 Unfortunately, many specialists are not aware that the inner ear balance function can nowadays be accurately recorded and analysed like a cardiogram does for the heart.

 It is meaningless to advise an Audiogram (hearing test) straightaway which only notes down the patient’s hearing status. The hearing portion of  the inner ear has nothing to do with balance portion of the inner ear, disease of which causes vertigo/ imbalance. It is carried out only for a complaint of deafness and/or tinnitus (noise in the ear) or if there is any abnormality detected on CENG testing.

Since 60 % of all balance disorders are in the province of the ENT specialist, opinion of an ENT specialist skilled in CENG recording and interpretation is mandatory.

When the vertigo especially imbalance does not respond to treatment prescribed after a CENG testing, a complete detailed neurological examination is done at the clinic as a second stage which includes checking  Higher functions, Cranial nerves (CNs), Sensory system, Motor system, Reflexes, Cerebellum   and  Fundoscopy.

There is nowadays an over reliance on the utility of Neuro-imaging (e.g. CT, MRI). They provide an evaluation of anatomy but not function. While being extremely helpful, they must be interpreted within the context of examination findings. A detailed clinical examination and meaningful tests and investigations can make a perfect diagnosis of a pathologic process, even if it is not seen on a particular radiological study. There are limits to what can be performed on even the most high tech imaging machine and therefore Radiology is  advised to confirm or exclude examination findings which make these unnecessary as a first investigation. These should be advised only after a careful examination and CENG.

The further investigations required may be – MRI brain scan with cervical & lumbar spine  screen, and  MR Angio scan -brain and neck blood vessels, Colour Doppler of neck blood vessels.

Also nerve muscle studies of the lower limbs may be advised for excluding disorders of proprioception –  (skin sensations and muscle function of the thighs, lower legs and feet). These include Electromyography (EMG), Nerve conduction velocity (NCV) & Somato sensory evoked potentials (SSEP).

Further reference may be required to a cardiologist for cardio vascular causes of vertigo, a psychiatrist for psychogenic vertigo, orthopedic specialist for cervical spine disorders etc.

Treatment of Vestibular Disorders

Basically there are the following options on how to treat patients with vestibular disorders:

Liberatory maneuvers to treat benign paroxysmal positioning vertigo ( B.P.P.V.) – Epley and Semont maneuvers

Vestibular rehabilitation therapy (VRT) - exercises for patient to perform, in those patients with unilateral or bilateral vestibular deficit or central vestibular lesions to improve the central compensation or substitution.

Medical treatment : A growing number of agents are available for the medical treatment of vestibular disorders. However, before initiating treatment, it is important to make the correct diagnosis and then to specifically treat the form of vertigo.

Psychological, psychiatric or behavioral therapy

Surgery:The role of surgery has diminished over the past years.