Basic ENT for common man

                                           

  To know about the ear and symptoms (complaints) of  the ear in general.

       First, let us know the parts of the ear. They are namely the external ear, middle ear and inner ear. External ear or outer ear consists of the pinna and the external auditory (ear) canal.  Pinna acts like a funnel, collects sound waves into the external ear canal. External canal is like a pathway and it sends sound waves to the middle ear.  The canal is about  two and a half cm long.  It ends at the tympanic membrane.

     Tympanic membrane or Ear drum separates the external ear from the middle ear. This membrane is a thin elliptical membrane,  only 0.1 mm (yes, you read it right- 0.1 milli meter only!) thick, which vibrates according to sounds and makes the ossicles  ( small bones ) of the middle ear vibrate.

     Middle ear is a six sided cavity. It has a roof, floor, outer wall, inner wall, front wall and a back wall.  The cavity's size is so small, the measurements being in millimetres- 2,6,8, and 18.  But, this small cavity contains three bones (ear bones are called as ossicles), a muscle and nerve and also an opening for a tube known as the Eustachian tube

     The Eustachian tube connects the middle ear cavity to the pharynx ( common cavity for the nose and mouth ). [ So, the ear is connected to mouth! ].

     Inner ear has a small ovoid bony chamber, containing fluid. Inside this bony exterior, there is a very thin membrane called Basilar membrane, over which the organ of hearing is situated. It is known as Organ of Corti.

       So far, we have seen about the pars of the ear. That is anatomy or structure of the ear. Now let us see how we hear. This is physiology or functioning of the ear. Sound is present around us every where, in the form of noise, voices of animals and humans, music etc. These sounds produce movement in the inner ear fluids. This stimulates the sensory cells in the Organ of Corti and an electrical impulse is produced and is transmitted to the brain by a nerve known as the Vestibulo- Cochlear nerve to the part of brain known as the auditory area and here the impulse is perceived as many types of sounds as noises, voices, music etc etc.

     Conduction of sound is by two ways .  Those are air conduction and bone conduction.  Air conduction is through the ear from the atmospheric air.  Bone conduction is from the vibration of the skull bones by sound. When one hears the far coming train, by keeping the pinna of the ear to the rail of the railway track, that hearing is by means of bone conduction.

      Functions of the ear are twofold - hearing and balancing. Inner ear plays an important role in the balancing of the body position. 

      Ok, after knowing about the structure and functioning of the ear, now we can learn about the common ear symptoms arising in day- to- day life and reasons for them, so that any one can understand about them and need not get panicked for trivial things.

     Thus the common ear symptoms (complaints) are pain, ear discharge, itching, changes in hearing , vertigo (giddiness), bleeding etc. Ear pain is called as Otalgia.  Pain may be from the external ear, tympanic membrane, middle ear or due to eustachian tube dysfunction.  Sometimes ear pain is from teeth, posterior (back) part of the tongue or throat .  Ear discharge is called Otorrhoea.  Discharge may be watery, clear fluid like, muciod, thick brown, pus like and/or foul smelling. 

    Bleeding through the ear is due to head injury.  Vertigo (hallucination of movement or subjective sense of imbalance). Patien feels either the patient is rotating or the environment is moving.  And one more symptom that would be noticed is involuntary (happening without one's control) eye movement. This is known as Nystagmus.

    As we deal with the symptoms one by one let us discuss about the commonly asked details of one topic, which my patients are so inquisitive about. That one is about hearing problems or hearing loss and whether hearing loud noises or using headphones might affect the hearing capacity.  And how the testing for hearing is done. For explaining this, the basics of the types, reasons, pathology of the condition are to be known a bit, that is just a touch of them. 

     So,

     Classification of hearing loss

      conductive type, sensory- neural type and mixed type. 

Other classification

 Congenital (since birth) is caused by failure to develop one or more parts of the auditory system, known as Aplasia, or an interruption in any stage in the process of development.

      And, degeneration of the parts of the auditory apparatus which have already developed, known as Abiotrophy. 

     Pathology of congenital deafness- 1- Of genetic origion

                                                            2- Embryopathies- mainly viral

          Sudden sensory- neural hearing loss, mainly due to localised or systemic vascular  (blood vessel) disease.  But, in vascular disorders deafness may be progressive or sudden.   And, viral- mumps, meningitis.  Rarely, acoustic neuroma ( presenting feature in 10% )

     There are many tests for hearing namely ,voice tests, tuning fork tests and audiometry. Tuning fork tests are done with a tuning fork of 512 Hertz frequency ( 512 cycles / second). Human ear is capable of hearing frequencies between 20 to 20,000 Hertz.   And there are many types of audiometric tests, like pure tone audiometry, speech audiomerty, Bekesy audiometry, tympanometry etc. The electronic device used for audiometry is called as audiometer.

     Next about the noise Induced Hearing Loss:-

     Usually sound seldom exceeds 100 dB. Conversation in quiet environment- 40 dB, telephone conversation- 40 to 70 dB. Loss occurs in industries, over amplification of sounds, aircraft noise, proximity of explosion, gunfire, noise of construction equipment etc. Exposure to  85 dB or more dB eight hours a day for a long time may result in hearing loss!  MUSIC- Delivered through amplifiers, head phones- Mild threshold shift in the lower frequencies which is not permanent. It means, not much dangerous to the audience  attending. (Similarly, the headset or earphones can be used in moderation. This moderation is as according to individual preferrance).  But, there is a risk of musicians developing sensory- neural hearing loss and tinnitus.  Tinnitus is a disorder of auditory perception, where the person hears sounds without any stimulation.  It is not a hallucination, where a person imagines to have hearing sounds.