2. Labyrinth (Inner Ear) :-
Definition :-
It is the inner most part of the ear.
Lying within the petrous part of the temporal bone.
Parts :-
1. Bony labyrinth
2. Membranous labyrinth
3. 1) Bony labyrinth :-
• Consists of series of bony cavities connected with one
another.
• It is filled with a fluid called “ Perilymph “.
• It consists of the following :
1. Semicircular canals
2. Vestibule
3. Cochlea
4. 2) Membranous labyrinth :-
• It lies in the perilymph of the bony part.
• It consists of sacs and tubes connected with each other and
contains a fluid called “ Endolymph “.
• It consists of the following :
1. Semicircular ducts
2. Utricle and Saccule
3. Cochlear duct
5.
6.
7. • ..Structure of the Inner Ear.mp4
• ..Model- Inner Ear and the Bony Labyrinth.mp4
8. Labyrinthitis :-
• The infection may affected the labyrinth in 3 stages.
1. Fistula formation (Para labyrinthitis) :-
o Without active clinical features.
o At this stage the infection does not reach the membranous
labyrinth.
2. Serous labyrinthitis (Reversible condition)
3. Purulent labyrinthitis :-
o With permanent deafness and loss of vestibular function.
9. Causes :-
• Infections
• Secondary to acute otitis media, dangerous chronic otitis media.
• TB
• Syphilitic otitis media
• Secondary to meningitis
• Viral ( due to mumps, measles, herpes zoster )
• Vascular causes ( thrombosis, embolism )
• Acoustic neuroma of internal auditory meatus
• Ototoxic drugs (like streptomysin)
• Meniere’s syndrome/disease (vertigo, deafness, tinnitus)
10. Clinical features :-
• Sensory – neural deafness
• Tinnitus
• Giddiness
• Vomiting
• Nystagmus
• Loss of balance
• Hearing is not markedly affected in serous labyrinthitis.
• Fistula test positive
• Purulent labyrinthitis (dead ear) leads to permanent total sensory neural
deafness. While the giddiness usually settles down in 3 to 4 weeks, as the
labyrinth of the other side takes over its function.
11. Treatment :-
• Mastoidectomy ( For first 2 stages )
• Labyrinthectomy ( For 3rd stage to drain pus )
• Antibiotics in full dose
13. Mastoidectomy
• Surgical removal of some or all of the mastoid process.
• Classification :-
1. Simple mastoidectomy
2. Radical mastoidectomy
3. Modified radical mastoidectomy
14. 1) Simple mastoidectomy ( Conservative or
Schwartze mastoidectomy ) :-
• This operation aims at draining the mastoid air cells by postaural
approach.
• It does not disturb the structure of the middle ear, hence the hearing is
unaffected.
Indication :-
1. Acute coalescent mastoiditis
2. Complications of mastoiditis
3. Tympanoplasty as a part of surgery
4. Decompression of the facial nerve
5. Decompression of the endolymphatic sac
6. Excision of an acoustic neuroma
17. 2)Radical mastoidectomy :-
• It is an operation in which the mastoid, middle ear and the
external auditory canal are converted into a single cavity by
lowering the wall between the mastoid and the external ear, and
removal of the remnants of the ear drum, malleus and incus.
• The stapes is not removed as the labyrinth gets exposed and
may be damaged.
• Conductive deafness may be a sequelae of this operation.
18. Indication :-
1. Cholesteatoma
2. Chronic osteitis of the mastoid
3. Chronic osteomyelitis of the mastoid
4. Tumors of the middle ear :benign
5. Labyrinthectomy
Complication :-
• Same as above , except conductive deafness is a sure
sequelae.
• Reoccurrence of the condition
19. 3)Modified Radical Mastoidectomy :-
• Which is similar to radical mastoidectomy, with the following
differences.
1) The following structures are not removed.
a) Tympanic membrane
b) Lower portion of malleus and incus.
2) There is no disease in the middle ear, and hence there is
no need for removal of any structures from there.
