Saturday, May 19, 2007

Tests for hearing loss

Rinne test

Normal hearing = POSITIVE. Air conduction is louder than bone conduction.
Conductive hearing loss = NEGATIVE. Bone conduction is better than air conduction.
Sensorineural hearing loss = POSITIVE because both bone air and bone conduction are equally reduced (NB: may need to mask normal ear to avoid a false negative from the opposite side).

Weber test

Normal hearing = sound comes from middle of forehead.
Unilateral conductive hearing loss = sound is loudest in AFFECTED ear because the ambient noise is picked up by the normal ear, masking the sound of the tuning fork on that side.
Unilateral sensorineural hearing loss = sound is loudest in UNAFFECTED (normal) ear.


  • "C:\Tam's docs\uni\Admin\year2\OSCE\Clinical skills summaries\ProcSkills\Procedural Skills.doc"

Tuesday, May 1, 2007


A sequestrum is a piece of dead bone that has become separated from normal/sound bone during the process of necrosis . It is a complication (sequelae) of osteomyelitis.

Pathological process of development of sequestra:

  • infection in the bone -> inflammatory exudate -> increase in intramedullary pressure
  • periosteum becomes stripped from the osteum -> vascular thrombosis
  • lack of blood supply -> bone necrosis
  • sequestra are formed

Due to the avascular nature of sequestra, antibiotics which travel to sites of infection via the bloodstream, poorly penetrate these tissues. Hence the difficulty in treating chronic osteomyelitis.

At the same time as sequestra are developing, new bone is forming (known as involcrum). Openings in the involcrum allow debris and exudates (including pus) to pass from the sequestrum via sinus tracts to the skin.

  • Image from