Pulsatile Nature of Glomus Tympanicum
Glomus tympanicum tumors are inherently pulsatile because they are highly vascularized paragangliomas arising from chromaffin cells of the middle ear paraganglia, and their rich arterial blood supply creates rhythmic pulsations synchronized with the cardiac cycle that are both visible on otoscopy and audible to the patient as pulsatile tinnitus. 1, 2
Pathophysiology of Pulsatility
Glomus tympanicum tumors are paragangliomas that arise from the paraganglia of the middle ear, specifically from chromaffin cells of the parasympathetic nervous system located along the tympanic plexus (Jacobson's nerve) on the promontory of the middle ear. 3, 4
The pulsatile nature results from the tumor's extremely high vascularity—these are among the most vascularized tumors in the body, with dense arterial networks that transmit cardiac pulsations directly through the tumor mass. 5
The tumor's location directly against the tympanic membrane allows mechanical transmission of these arterial pulsations, making them both visible to the examiner during otoscopy (as a pulsating reddish mass) and audible to the patient as rhythmic tinnitus synchronized with their heartbeat. 1, 2
Clinical Presentation
Pulsatile tinnitus is the most common presenting symptom of glomus tympanicum, occurring in 61.5-100% of patients, and is the chief complaint in the majority of cases. 6, 3
On otoscopic examination, glomus tympanicum appears as a reddish or reddish-blue vascular retrotympanic mass behind the tympanic membrane, with visible pulsations that are pathognomonic for this diagnosis. 1, 2, 7
Conductive hearing loss is the second most common symptom, occurring when the tumor mass interferes with ossicular chain mobility or fills the middle ear space. 3, 4
Some patients present with pseudo-low-frequency hearing loss (PLFHL) that resolves immediately after surgical tumor removal, likely due to the tumor's mass effect on the tympanic membrane and ossicular chain. 6
Diagnostic Approach
High-resolution CT temporal bone without contrast is the first-line imaging study when glomus tympanicum is suspected based on otoscopic findings of a vascular retrotympanic mass. 1, 2, 7
CT temporal bone demonstrates the characteristic soft tissue mass on the promontory of the middle ear, absence of bone erosion into the jugular bulb or carotid canal (which would indicate glomus jugulare or jugulotympanicum), and intact ossicular chain. 1
MRI with contrast can be helpful in difficult cases to better characterize the tumor's extent and vascularity, showing intense enhancement on T1-weighted post-contrast images and the characteristic "salt and pepper" appearance on T2-weighted images due to flow voids. 3, 4
Never perform a biopsy of a suspected vascular retrotympanic mass without imaging confirmation, as inadvertent biopsy of an aberrant internal carotid artery or dehiscent jugular bulb can cause catastrophic hemorrhage. 1
Treatment
Surgical removal via transcanal approach is the gold standard treatment for glomus tympanicum, with complete tumor removal achieved in nearly 100% of cases, immediate resolution of pulsatile tinnitus, low complication rates, and minimal morbidity. 6, 3
Preoperative embolization with selective tumor denaturation using 96% ethanol performed 24 hours before surgery significantly reduces intraoperative hemorrhage, with studies showing complete disappearance of tumor blush on post-embolization angiography and median tumor necrosis of 69.2%. 5
The transcanal approach allows complete tumor removal while preserving the ossicular chain intact in most cases, maintaining acceptable hearing levels postoperatively. 3
Radiation therapy has been advocated in the literature for elderly patients with multiple comorbidities who cannot tolerate surgery, though surgical removal remains superior for tumor control and symptom resolution. 3, 8
Recurrence after complete surgical removal is rare, occurring in less than 6% of cases even with long-term follow-up (9+ years). 3
Critical Clinical Distinctions
Glomus tympanicum is confined to the middle ear space and arises from the promontory, whereas glomus jugulotympanicum originates from the jugular bulb and extends into the middle ear, showing bone erosion of the jugular foramen on CT. 1
The pulsatile tinnitus from glomus tympanicum resolves immediately after surgical removal in 100% of cases, confirming the mechanical nature of the pulsations transmitted through the vascular tumor mass. 6, 5
Glomus tympanicum occurs predominantly in women (female-to-male ratio approaching 100% in some series) and typically presents in the fifth to sixth decades of life. 3, 8
Common Pitfalls
Missing the diagnosis by dismissing pulsatile tinnitus as benign without performing otoscopy—detailed otoendoscopic examination of the middle ear is mandatory in all patients presenting with pulsatile tinnitus and conductive hearing loss. 6, 4
Misdiagnosing glomus tympanicum as cholesteatoma, particularly when the tumor causes otorrhea or external auditory canal involvement, can lead to inappropriate surgical planning and intraoperative hemorrhage. 4
Failing to use intravascular contrast agents during CT or MRI imaging makes differential diagnosis difficult and may miss the characteristic intense enhancement pattern of glomus tumors. 4