Glomus Jugulare

• Pulsatile tinnitus and conductive hearing loss. MEN I & II.
• Aggressive-appearing hypervasular jugular fossa soft-tissue mass extending into middle ear cavity with permeative bony erosion
• Zellballen pattern of chief cells
• Rarely malignant; regional nodal metastasis.

Description

Glomus jugulare tumours are paragangliomas located at the skull base, arising from the chief cells of the paraganglia within the jugular bulb, which is part of the jugular vein. Paraganglion cells, integral to the extra-adrenal neuroendocrine system, regulate body responses to hypoxia, hypercapnia, and hypoglycaemia through their chemoreceptor functions. These tumours are highly vascular and typically benign, though they can be locally aggressive and invade nearby bone and soft tissues. Glomus jugulare tumours are noted for their association with the parasympathetic nervous system. They are the second most common head and neck paraganglioma¹.

Pathogenesis

The exact pathogenesis of glomus jugulare tumours is not fully understood but is thought to involve genetic mutations that lead to abnormal cell growth of the paraganglia located at the jugular bulb. These tumours can occur sporadically or as part of inherited syndromes such as Multiple Endocrine Neoplasia (MEN) types II and III.

Subtypes

Whilst not exactly a subtype, a similar entity known as a jugulotympanic paraganglioma is defined by some authors as paragangliomas which cannot be definitively classified as jugular or tympanic in origin².

Epidemiology, Risk Factors & Associations

• Most commonly diagnosed in middle-aged adults.
• More frequent in females.
• Majority are sporadic, up to 40% though to be hereditary
• Association with genetic syndromes
  • Succinate dehydrogenase mutations (primarily SDHC and SDHD mutations)
  • Multiple endocrine neoplasia
  • Neurofibromatosis type 1
  • von Hippel-Lindau syndrome
• May be associated with other glomus tumours, e.g. carotid body paragangliomas (glomus caroticum).

Clinical Features

• Pulsatile tinnitus – most common feature, often described as a whooshing sound that is synchronous with the heartbeat.
• Hearing loss – typically conductive in nature, resulting from middle ear involvement.
• Lower cranial nerve deficits: Including hoarseness, difficulty swallowing, and tongue weakness, due to tumour compression or invasion.
  • Vernet Syndrome – Motor paralysis of cranial nerves IX, X and XI
  • Collet-Sicard Syndrome – Vernet syndrome with additional involvement cranial nerve XII
  • Horner Syndrome – Ptosis, miosis, anhidrosis.

Complications

• Intracranial extension can lead to increased intracranial pressure and neurological deficits.
• Local invasion can cause destruction of the temporal bone and other skull base structures.
• Rare malignant transformation: Regional nodal metastasis. Distant metastasis is extremely uncommon.

Pathological Features

Histopathology

• Macroscopic: Well-circumscribed, reddish-brown tumour.
• Microscopic: Nested or “Zellballen” pattern of chief cells, surrounded by a fibrovascular stroma.

Radiological Features

General Features

• Enhancing soft tissue mass with aggressive expansion and permeative moth-eaten bony erosion of the temporal bone.
• May extend into the middle ear, sometimes referred to as a glomus jugulotympanicum
• Jugulotympanic paragangliomas are defined as paragangliomas which cannot be definitively classified as jugular or tympanic in origin.
• MRI best modality for demonstrating tumour extent, especially intracranial extension which changes management
• CT best modality for demonstrating bony erosion, usually essential for pre-operative planning.

CT

• Non-contrast (bone window): Permeative bone erosion at the skull base. Erosion of the jugular spine and caroticojugular spine.
• C+ Arterial: Avid-enhancement/vascular blush, usually indicated for preoperative embolisation to reduce intraoperative bleeding.

MRI

• Typical salt-and-pepper appearance seen on both T1 and T2. Salt represents the haemorrhage or slow flow, and pepper represents the flow voids due to high vascularity.
• T1: Isointense to muscle, hypointense to brain parenchyma.
• T2: Heterogeneous signal intensity with areas of high flow voids.
• T1 Gd+: Avid enhancement.
• DWI/ADC: Typically does not show restricted diffusion unless there is necrotic or cystic change.

DSA

• Intense tumour blush.
• Feeding vessel commonly the ascending pharyngeal artery.
• Early venous drainage due to intratumoural shunting

Grading and Staging

Not applicable.

Diagnosis

Diagnosis is usually made based on clinical symptoms, imaging findings, and occasionally biopsy if the diagnosis is uncertain.

Differential Diagnosis

Imaging-based

• Schwannomas: Particularly of the vestibular type, may present similarly but typically involve the internal auditory canal. No internal flow voids/salt and pepper appearance. Fusiform-shaped tumour with intramural cysts. No dural tail/flow voids. Smooth bony margins.
• Meningioma: Another common skull base extradural tumour with centrifugal spread pattern, hyperostotic or permeative sclerotic bone changes, enhancing dural tails. No flow voids. Calcifications are commonly seen.
• Glomus tympanicum: Enhancing soft-tissue mass centred over the cochlear promontory and confined to tympanic cavity, also causing pulsatile tinnitus. Typically smaller and less aggressive, sparing the jugular bulb and ossicles. Enhancement differentiates the mass from obstructive secretions. Most common tumour of middle ear.
• Glomus jugulotympanicum: A paraganglioma which cannot be definitively classified as jugular or tympanic in origin characterised by invasion of both the jugular foramen and middle ear, without clearly arising from either of these spaces.
• Glomus vagale: Arises from paraganglia in nodose ganglion of the vagus nerve in the nasopharyngeal segment of the carotid space. The mass displaces the carotid artery anteromedially, jugular vein posterolateral and does not splay the carotid bifurcation.
• Metastatic disease: Can mimic the imaging appearance but usually has a known primary cancer source.
• High-riding or dehiscent jugular bulb
• Skull-base chondrosarcoma: Usually involves the petro-occipital fissure.

Clinically-based

• Glomus tympanicum: Also causes pulsatile tinnitus. Appears as red-bluish, pulsatile mass on otoscopic examination.

Masses on otoscopy

Colour and Location	Most Likely Mass
Red mass; anteroinferior	Glomus tympanicum
Red mass; crosses the tympanic membrane from posterior to anterior	Aberrant ICA
Blue mass; posterior	Dehiscent jugular bulb
White mass; inferior	Congenital cholesteatoma
White mass; superior	Facial nerve schwannoma

Management

• Surgical resection is the treatment of choice for symptomatic or growing tumours, although complete removal can be challenging due to the tumour’s location and vascularity.
• Radiation therapy including stereotactic radiosurgery, is an option for patients who are not candidates for surgery or for residual or recurrent disease.
• Preoperative embolisation can be utilised to reduce vascularity and facilitate surgical resection. The ascending pharyngeal artery is a common feeder artery.

References

1. Smith, J.D., Harvey, R.N., Darr, O.A., Prince, M.E., Bradford, C.R., Wolf, G.T., Else, T. and Basura, G.J., 2017. Head and neck paragangliomas: a two‐decade institutional experience and algorithm for management. Laryngoscope investigative otolaryngology, 2(6), pp.380-389. ↩︎
2. Thelen, J. and Bhatt, A.A., 2019. Multimodality imaging of paragangliomas of the head and neck. Insights into imaging, 10, pp.1-9. ↩︎