Neurotology - A Closer Look at the Neurological Aspects of the Ear

Introduction

Neurotology is closely related to otology. Otology refers to the normal pathological structure and functions of the ear. Otology and neurotology are further specialized in pathological conditions of the ear and related structures. Neurotology encompasses more complex surgery of the inner ear.

What Is Neurotology?

Neurotology is a branch of medical science that studies and treats neurological disorders of the ear. It is a subspeciality of otolaryngology-head neck surgery and neurology. This discipline is specialized in diagnosing and treating diseases of balance and the auditory system.

What Is the Anatomy of the Ear?

The ears are organs that help in hearing and balance. The ear consists of three parts listed below:

• Outer Ear: Consists of a pinna or auricle and ridged cartilage and skin. This contains a gland that produces ear wax. A funnel-shaped canal (external auditory canal or tube) leads to the eardrum or tympanic membrane (which divides the external ear from the middle ear).

• Middle Ear: Middle ear begins at the other end of the eardrum. Three tiny bones are present in this area: the malleus, incus, and stapes, called ossicles. It also contains a eustachian tube that helps balance the pressure in the middle ear.

• Inner Ear: Inner ear contains the cochlea, vestibule, and semicircular canals. The cochlea is the hearing organ with two chambers lined with tiny hairs and filled with fluids. The cochlea has the nerves for hearing. Vestibules have receptors for balance. Semicircular canals have receptors for balance.

How Does the Ear Function?

The hearing process starts at the outer ear. Sound waves travel through the external auditory canal and strike the eardrum (tympanic membrane). The vibration occurs at the eardrum when sound waves strike. Then vibrations are passed to tiny bones(ossicles) in the middle ear. These ossicles amplify the sound and send it to the cochlea, a part of the inner ear. In the inner ear, sound waves are converted to electrical impulses. These impulses are transmitted to the brain through the auditory nerve. The brain then translates these impulses as sound.

What Are the Conditions Dealt With Neurotology?

A neurotologist is a specialist who diagnoses and medically and surgically manages neurological diseases of the ear and brain.

Some conditions that are dealt with under neurotology are:

• Vertigo or head spinning.

• Imbalance or instability.

• Disorder of hearing related to the inner ear and auditory nerve or neural pathways in the brain.

• Tinnitus (A buzzing sound in the ear or head).

An ENT specialist cannot treat these conditions. Still, a multi-disciplinary approach involving a team of doctors such as a neurologist, ENT specialist, psychiatrist, physiotherapist, and doctor of internal medicine is necessary. Sometimes, neurosurgeons, ophthalmologists, and cardiologists may be involved. However, only some specialists working in one table are feasible. Hence one person is specialized in treating these conditions is known as a neurotologist.

Neurotology comprises all disorders that involve temporal bone, structures in the base of the skull and cerebellum, the brain stem, the midbrain, cranial nerves, the limbic system, and the hippocampus in the brain. Unfortunately, treating all these disorders is beyond an ENT specialist's knowledge level. A neurotologist can treat an ear-related severe problem that is affecting the balance or hearing, and conditions treated by a neurotologist are listed below:

• Complex Hearing Diseases: Ear disorders, if not treated, may result in long-term and debilitating problems like infection, hearing loss, vertigo (dizziness), facial paralysis, or weakness.

• Hearing Loss: Neurotologists help in such conditions by treating with hearing aids and using other methods.

• Acoustic Neuroma ( Tumor In or Near The Ear): Noncancerous growths occurring on nerves responsible for balance and hearing.

• Chronic Ear Infection: Chronic ear infections lead to complications like cholesteatoma (cyst in the ear), tympanic membrane perforation, and hearing loss.

• Vertigo: In this condition, individuals experience the spinning of the environment around them. Complicated vertigo, which does not improve after treatment.

• Otosclerosis: In this condition, the third bone of the ear does not move as well as it does, resulting in hearing loss due to conduction.

• Congenital or Acquired Ossicular Chain Fixation or Discontinuity: Tiny bones in the inner ear may be malformed from birth or later in life due to trauma, surgery, or infection.

• Osteoma: A benign tumor of bones in the inner ear.

• Glomus Tumor: A rare temporal bone or middle ear tumor.

• Tympanosclerosis: Chronic ear infections may produce scar tissue, calcium deposits, or a new bone formation in the middle ear.

What Are the Diagnostic Tools in Neurotology?

There are many advanced techniques and procedures to diagnose conditions affecting the ear and surrounding structures. They are listed below:

• Pure Tone And Speech Audiometry: Measures how an individual can hear.

• Acoustic Immittance, Tympanometry, And Acoustic Reflex Studies: A tiny probe is used to check how well the structures and muscles in the middle ear are working.

• Otoacoustic Emissions: A microphone measures how well the hair cells are working.

• Auditory Brainstem Response Testing (ABR): Evaluate the nerves that run from the inner ear to the brain.

The following diagnostic tests are done for imbalance and dizziness:

• Audiologic Assessment: Inner ear function is evaluated.

• Posturography: This assesses how an individual maintains balance.

• Videonystagmography (VNG): Evaluates how an inner ear senses an individual’s motion and stable vision.

• Rotational Chair Test: To check the extent of weakness in the inner ear.

• Vestibular-Evoked Myogenic Potentials (VEMPS): To test how the inner ear senses gravity and various head and body movements.

The following tests are done to check skull-based tumors:

• Magnetic Resonance Imaging (MRI): Done to get a clear image of nerve tissues and other structures of the brain stem and posterior brain.

• Computed Tomography (CT): This imaging provides a clear picture of any mass present or fluid-filled and signs of stroke in the brain.

• Bone Scan: To detect bone tumors and their spread in the body.

• Positron Emission Tomography (PET): It can detect cell changes as they grow.

What Are the Treatments in Neurotology?

Neurotology is very closely related to otology, but added skills are with a neurotologist to treat the skull, the parts of the brain, and the nervous system related to hearing and balance. They treat conditions like acoustic neuroma, glomus tumors (benign soft tissue tumors resembling smooth muscle), other conditions of the skull, and surgery of cochlear implants.

1. Tympanoplasty: This procedure is done to repair damaged eardrums or ear bones.

2. Mastoidectomy: It is used to remove the chronic infection or cholesteatoma.

3. Cochlear Implantation: This procedure is done for hearing loss to regain the hearing process. Neurotologists also do bone anchoring implants.

4. Surgery:

• Surgical removal and stereotactic radiosurgery of acoustic neuroma.

• Excision of tumors (cancerous and noncancerous).

5. Repair:

• Repair superior canal dehiscence (incomplete closure of the bony canal in the inner ear).

• Repair of spinal fluid leaks.

6. Endoscopic Ear Surgery: Transcanal endoscopic ear surgery (TEES) is done to avoid an incision behind the ear and an opening in the skull. Neurotologists do the following procedures:

• Ossiculoplasty: Reconstruction of tiny bones in the ear to regain hearing process.

• Stapedectomy: Removal and reconstruction of stapes bone to regain hearing loss.

• Tumor Removal: Removal of cancerous and noncancerous tumors.

• Tympanoplasty: Repair of a perforated eardrum.

• Cyst Drainage: Drainage of cysts in the inner ear can be done using transcanal endoscopic ear surgery (TEES).

Conclusion

Hearing is an important function in the human body. If any disturbance or complete loss of hearing occurs may affect the quality of life among humans. Hence it is important to know in detail about the structures and functions of the ear. Furthermore, learning about the conditions helps us seek the doctor's help at the earliest. Early diagnosis always results in effective treatment. This, in turn, helps achieve a good quality of life preferred by all humans.