What are the clinical features of perilymph fishula? How do you investigate and confirm the diagnosis of perilymph fistula.
Unlike labyrinthine fistula, perilymph may leak from the inner ear to the middle ear either from rupture of the stapediovestibular joint, fracture of the stapes footplate or tearing of the round window membrane.
These are more often from the oval window.
Risk is more with Stapedectomy compared to stapedotomy (Stapedectomy > stapedotomy)
The surgeon creates a fistula at every stapedectomy operation and seal the opening.
In most operation there is enough surgical trauma to the oval window microperiosteum to lead to the production of an inflammatory repair envelope around the prosthesis sealing the opening.
Fistula more common c interposition technique but hearing better with prosthesis.
Persisting Conductive hearing loss after operation –Peri Lymphatic Fistula
2° or acquired fistula
Spontaneous (no recognizable aetiological)
SYMPTOMS AND SIGNS
History of head injury or stapes or other middle ear surgery or other events associated ↑Intra Cranial Pressure such as coughing, straining / aviation/ diving.
Unsteadiness and dizziness c marked positional element which tends to persist until the fistula is closed either by spontaneous healing or by surgery.
Hearing loss: persistent or fluctuating: Sensory Neural Hearing Loss /Conductive Hearing Loss / mixed.
Sometime present c recurrent meningitis or CerebroSpinal Fluid behind the TM.
Examination of ear: Unremarkable c rarely TM retraction or evidence of middle ear fluid
Fistula text: is usually, but not always negative(1/3) (This test is for a third opening into the inner ear) Fistula test with electro-nystagmography – Quick phase always from the effected ear accurate but negative response doesn’t rule out diagnosis of fistula.
Positional nystagmus: The characteristics that differentiate the positional nystagmus from BPPV are:
There is either a short or no latent period.
Nystagmus is not violent as in BPPV.
The duration tends to be longer c the nystagmus fatiguing slowly or not at all
The nystagmus rarely reverses direction when the patient is bought to the sitting position.
The nystagmus doesn’t necessarily beat toward the involved ear.
The nystagmus is only occasionally rotary.
Initially: pure tone SNHL in the low frequencies
Flat loss which fluctuates & Recruitment ±
Initially speech discrimination fluctuate c the pure tone threshold, but later they may be disproportion lower than expected when compared to stapedius reflex threshold.
Frazier’s test– an improvement in pure tone threshold when lying for 30 minutes compared to sitting.
Romberg test may be +ve
Canal paresis or hypoactive response
After stapedectomy high incidence of ↓ caloric response.
Caloric test: little value in diagnosis fistula.
May reveal a directioned fixed positional nystagmus but this cannot be relied upon.
Diagnosis by radioactive tracer method/ Fluorescein
Radioactive indium -111 DTRA is injected into the lumbar subarachnoid space.
The demonstration of ↑ radioactivity in nasopharyngeal secretions strongly supports the fistula.
MRI and High Resolution CT (HRCT): low predictive value
Fluid in non diseased mastoid or m/e and in round window niche on T2 weighted MRI.
Diagonisis can be confirmed only by surgical exploration
Bed rest for minimum 5 days c the head of the bed elevated 30-40°.
Sedation and faecal softeners should be prescribed.
Symptoms settled – limit activity for further 10 days and avoid exertion.
Indication : If medical treatment fails, if symptoms persist for over 1 month.
Permeatal: Standard tympanotomy
Elevation of tympanomeatal flap
Inspect middle ear avoiding trauma as it can produce serous ooze.
If ↓d/A: Valsalva manouevre may help identify leak. Inspect round window and oval window.
If ↓G/A: Identification of the site of leak.
Place the patient in Tredelenberg head down position
↑ Ventilatory pressure.
Use of intrathecal fluorescein like in Cerebrospinal Fluid leak (controversial)