ENT NOTES : PINNA ANATOMY

    PINNA 

      P)inna is made of yellow elastic cartilage which is again covered by skin .Skin is closely attached to cartilage on lateral surface but loose on medial ( back ) surface . 

Nerve supply of pinna :   Lobule of pinna : Greater auricular nerve . Medial surface : Lesser occipital nerve . Lateral surface : Auriculotemporal nerve . Concha of pinna : Auricular branch of vagus and few fibres of facial nerve .     

 Cauliflower are or boxer's ear : Post traumatic deformity = Subperichondrial hemorrhage 

External Auditory Canal ::  24 mm in length . Outer 8mm cartilagenous , inner 16 mm bony .

EAC is lined by skin . Outer part has hair follicles and ceruminous gland . 

EAC skin migrated outwards and hence brings the dead skin and tissues out . If this migration is absent , it leads to accumulation of dead tissues and wax in EAC as a large expansile mass 

 It can damage facial nerve too . This condition is called keratosis obturans . Treatment is cleaning of EAC in every 6 months . 

Blockage of EAC due to wax =30 db hearing loss . Tratment= Syringing . Direction of syringing is = Postero superior .

 Live insect in Eac , what to do ? 1st : Oil in EAC to kill it then remove it . 

Isthmus of EAC is the narrowest part . It lies 6 mm laterla to tympanic membrane . Any foreign body lying beyond isthmus will get impacted . 

Fissure of Santorini  : Natural defect in cartilagenous EAC . Clinical importance = infection can travel from EAC to parotid gland .

Fissure of Huschke : Natural defect in bony EAC . 

Directon of EAC = Inward Downward and Forward . SO Direction of pulling =  Upward , Outward and Backward . 

NERVE SUPLLY OF EAC : Anterior wall and roof : Auriculotemporal nerve . 

                                           Posterior wall and floor : Auricular branch of vagus ( Also called Arnold's or Alderman's nerve , stimulation of this nerve leads to cough .)

                                           Posterosuperior part : Sensory divison of facial nerve ( nerve of Wrisberg )

Note : Loss of sensation in posterosuperior part EAC is a feature of acoustic neuroma . This is known as Histelberger's sign .

Diseases of external ear :: 

 Otitis Externa or  Telephonist Ear : Infection of skin of EAC . 2 types : 1) Diffuse and 2) Local 

Furunculosis : Diffuse is also known as furunculosis = Staphylococcal infection  of single hair follicle, seen in outer part of the canal , painful condition .Treatment ; Ichthammol ( antiseptic ) and Glycerin ( reduces oedema ) packing . 

 Note: Diabetic + ext ear furunculosis= Rx : Oral flucloxacillin