Findings:
- Confluent with the caudoventral aspect of the right ethmoid turbinates, and extending caudally into the region of the right sphenopalatine sinus, there is a large, lobular, non-contrast enhancing and mildly fluid-cavitated mass, which is mostly hypointense on T2 and T1w sequences. On the gradient echo sequence, at the location of the mass, a focal signal void with moderate blooming (susceptibility artifact) is identified.
- The mass dorsally displaces and mildly compresses the right optic nerve, rostral to the chiasm, as it courses along the dorsal aspect of the sphenopalatine sinus.
- Filling the rostral aspect of the right rostral maxillary sinus, and in the caudodorsal aspect of the right conchofrontal sinus, there is gravity dependent, non-contrast enhancing, material with a well-defined air-fluid meniscus. This material is T2 hyperintense and has intermediate signal intensity on the T1 w sequences.
- There is mild right-sided mucosal thickening and contrast enhancement of the rostral right nasal concha, medial right ethmoid turbinates, to the level of the cribriform plate.
Conclusions:
- Right sided nasal mass associated with the ethmoid turbinates and shenopalatine sinus, with associated compression of the right optic nerve. An ethmoid hematoma with chronic hemorrhage is the primary differential.
- Right rostral maxillary and chonchofrontal sinus fluid, and right nasal mucosal thickening. Consider rhinitis/sinusitis and or paranasal sinus hemorrhage.
Follow-up:
- The mass could not be visualized endoscopically.
- Standing right frontonasal sinus flap surgery for partial removal of the mass
- Histopathology of the mass:
- Hemorrhage, multifocal, chronic, marked, with granulation tissue formation, frontal / maxillary sinus respiratory mucosa –> confirmed hematoma
- Recheck MRI one month later showed persistence/progression of the remainder of the mass:
- At that time, a maxillary sinus flap surgery was made to access the rostral end of the sphenopalatine sinus, and a laryngotomy was performed for a ventral approach to the caudal aspect of the sphenopalatine sinus. Blood obscured the mass, limiting the ability to fully remove it.
- Post-opoerative CT showed marked reduction of the mass:
A little bit more…
- The etiology of ethmoid hematomas remain unknown. Progressive ethmoid hematomas is estimated to have a 0.03% to 0.04% prevalence and is reported to affect horses from 4 weeks to 20 years of age, with a mean of 9.9 years according to a case review (Stich et al.). A higher incidence in older horses is thought likely.
- Usually unilateral but may expand into the contralateral side (Stich et al).
- Pathophysiology (Stich et al.):
- Hemorrhage into the submucosa of an endoturbinate (ethmoid labyrinth) results in hematoma formation –> repeated hemorrhagic events causes hematoma to expand and subsequently stretches/thickens the mucosa to form a capsule.
- Excessive pressure results in regional distortion and destruction of soft tissue.
- Bone and mass/regional tissues and blood vessels can tear resulting in ipsilateral epistaxis.
- In most cases, radiographs can be helpful for the identification of a nasal/paranasal mass (Stich et al, Manso‐Díaz et al.)
- Cross sectional imaging allows for better localization of the mass to help direct therapy (Stich et al.)
- MRI’s superior soft tissue detail provides greater anatomic details and an adequate evaluation of different sites involved (Stich et al, Manso‐Díaz et al.).
- CT allows enhanced visualization of the surrounding osseous structures (Manso‐Díaz et al.).
- Contrast administration may be helpful to distinguish non-contrast enhancing ethmoid hematomas from neoplasia (Manso‐Díaz et al.)
- MRI features of ethmoid hematomas (Tessier et al., Careddu et al.):
- Well-delineated and encapsulated mass(es), which contacts the ethmoid turbinates
- Hypointense on T1 compared with temporal muscles, and hypo- or hyperintense on T2/STIR. In acute stages, hematomas may have a higher T2w signal and appear more heterogenous and hypointense with chronicity.
- Signal void may be observed on GE T2* sequences
- Better outcome with early lesions recognition and treatment initiation (Stich et al., Careddu et al.).
- Treatment techniques may include (Stich et al.):
- Surgical excision through a frontonasal bone flap
- Surgical excision with cryotherapy of the base of the mass
- Cryotherapy of the mass without surgical excision
- Transendoscopic Nd:YAG laser photoablation
- Laser excision through a frontomaxillary bone flap
- Transendoscopic intralesional injection of 10% formalin.
References:
- Careddu, Giovanni Mario, et al. “Magnetic resonance imaging features of progressive ethmoid hematoma in 2 horses.” Vet Ital 52.1 (2016): 31-35.
- Tessier, Caroline, et al. “Magnetic resonance imaging features of sinonasal disorders in horses.” Veterinary Radiology & Ultrasound 54.1 (2013): 54-60.
- Stich, Kelly L., Bonnie R. Rush, and Earl M. Gaughan. “Progressive ethmoid hematoma in horses.” Compendium 23 (2001): 1094-1103.
- Manso‐Díaz, G., et al. “Application and indications of magnetic resonance imaging and computed tomography of the equine head.” Equine Veterinary Education 33.1 (2021): 31-46.
- Manso‐Díaz, Gabriel, et al. “Magnetic resonance imaging characteristics of equine head disorders: 84 cases (2000–2013).” Veterinary Radiology & Ultrasound 56.2 (2015): 176-187.
