When can trephination be used to treat sinusitis?

When radiography and nasal endoscopy are inconclusive as to the aetiopathogenesis of sinusitis, sinoscopy is the next likely investigative procedure [1]. It is well tolerated in standing sedated horses [2]. It has been shown to provide useful diagnostic information in 67–100% of cases [3–5]. Currently, the optimum route for fenestration of the ventral conchal bulla (VCB) is under sinoscopic guidance through the conchofrontal sinus (CFS), permitting adequate observation of the rostral maxillary sinus (RMS) and ventral conchal sinus (VCS) in 88–95% of cases [3,6]. The technique and equipment required are well described by O’ Leary and Dixon [7]. It is important to investigate the 2 rostral sinus compartments (RMS and VCS) as they were found to be involved in 61% and 54% in one study [3].
Sinus trephination is indicated for sinoscopy, placement of a lavage tube, endoscopic fenestration of the VCB, sinoscopically guided sinus surgery (mass biopsy, removal of inspissated pus, conchal bone sequestrate, small sinus cyst, fungal plaques, formalin injection) or removal of small intrasinus progressive ethmoid haematomas.
The most frequent intraoperative complication of the procedure associated with fenestration of the VCB is excessive haemorrhage limiting visualisation and occurring in approximately 20% of cases [6]. Anecdotal reports of reducing haemorrhage from fenestration of the VCB, especially in chronic sinusitis cases can be aided by prior lavage of the structure with adrenaline and use of a ligasure to fenestrate the bulla and transendoscopic laser diode.
Post operative complications of sinoscopy reported by Dixon et al. [3] include sinocutaneous fistula (n = 1), nasofrontal exostosis (n = 2) and delayed onset cellulitis (n = 1) in a total of 200 cases. However, these complications typically occur more frequently after sinusotomy [2,5,8].
A large study by Dixon et al. [9] found sinoscopy to be therapeutically useful with longer term sinus lavage in 43% of cases. Within the primary sinusitis group, all 13 cases which did not have inspissated pus resolved after fenestration of the VCB. Within the inspissated primary sinusitis group 4/9 resolved with sinoscopy, lavage and endoscopically guided removal of the inspissated exudate. The other 5 requiring an osteoplastic sinus flap. An earlier study reported 77% of primary sinusitis cases to respond favourably to sinoscopy and lavage [5].  […]