Describe myringitis and acquired stenosis of the external canal.

Myringitis

• Myringitis is inflammation of the tympanic membrane itself, either as part of otitis externa or media, or as a primary condition.
• Two forms matter clinically: bullous myringitis and granular (chronic) myringitis.
• Bullous myringitis (myringitis bullosa haemorrhagica) — an acute condition in which haemorrhagic blebs or bullae form between the outer epithelial and middle fibrous layers of the drum and the adjacent deep canal
• It is viral, following an upper respiratory infection — influenza is classical — and mycoplasma pneumoniae is the important association, so the presence of bullous myringitis should prompt a question about a preceding atypical pneumonia
• Features — the cardinal symptom is sudden, severe and often excruciating pain, out of all proportion to the findings; blood-stained serous discharge when a bulla ruptures, after which the pain is dramatically relieved; and mild hearing loss
• Sensorineural hearing loss occurs in a proportion, particularly with mycoplasma, so audiometry should be performed rather than assuming a conductive loss

Canal Stenosis

• Acquired stenosis of the external canal is narrowing by fibrous tissue or bone, and is not the same as congenital atresia
• Causes — chronic or recurrent otitis externa, which is the commonest; granular myringitis; trauma and burns; previous ear surgery, particularly meatoplasty; radiotherapy; chronic dermatological disease; and post-inflammatory scarring
• Two types — fibrous (soft tissue) stenosis, in which a fibrous plug or web forms medially, often with trapped skin and debris medial to it; and bony stenosis, from exostoses or post-inflammatory new bone
• Features — conductive hearing loss, which may be severe if the canal occludes completely; recurrent infection and discharge from trapped debris; and inability to examine the drum, which is what brings it to attention
• The important danger IS the entrapped skin medial TO the stenosis.
• Investigation — audiometry, and high-resolution CT to assess the length and nature of the stenosis, the state of the middle ear, and to exclude cholesteatoma medial to it
• Treatment — canalplasty: excision of the fibrous plug or drilling of the bony narrowing, widening the bony canal, and lining it with a split-thickness skin graft to prevent recurrence, with prolonged packing or stenting
• Meatoplasty may be needed to widen the cartilaginous opening as well
• Restenosis is common, and is the principal difficulty; adequate widening, complete skin coverage and long-term follow-up are what reduce it