Carotid body tumours
These are tumours (both cancerous and non-cancerous) that arise in the region where the carotid artery, the main artery that supplies one half of the brain, divides. They develop from a specialized nest of cells that secrete chemicals that control responsible for control of blood pressure and respiration. Often they are in close proximity to the artery, but sometimes they can invade the vessel wall, making the operation to remove them complex and technically challenging.
How common is it?
These are uncommon, accounting for less than 1% of all head and neck tumours. However with good quality imaging, they are often detected incidentally on ultrasound or CT, even when they do not produce symptoms.
What are the symptoms?
These can often be detected on imaging performed for other complaints. These patients often present with a lump in the neck. Rarely patients can present with anaesthesia of the throat, hoarseness of voice, difficulty swallowing, shoulder dysfunction and reduced tongue movement if the adjacent cranial nerves (glossopharyngeal, vagus, spinal accessory and hypoglossal nerves) are involved.
What causes it?
Familial causes are very rare, the only established causation is living at high altitudes with low oxygen levels in the air.
How do you diagnose it?
These tumours have a characteristic appearance and location on imaging, and can be diagnosed through imaging. CT or MRI is the imaging investigation of choice. In large or complex lesions, additional scans that determine blood flow to the brain, like digital subtraction angiography or a balloon test occlusion, may be required. These are performed when you require surgery and surgeon needs to determine if the carotid artery can be sacrificed without interruption to the blood supply of the brain (this depends on collaterals or additional channels from the carotid artery of the opposite side). It is also required when the plan is to perform a reconstruction of the carotid artery if part of the vessel needs to be removed due to involvement by the tumour. Biopsy is never performed as they have a high chance of bleeding, which can be life threatening.
How do you treat it?
In small discrete lesions, surgery is the treatment of choice. The complexity of the operation depends on the size, location and the extent of involvement of the carotid artery. Wherever possible, the goal is to remove the tumour without disrupting the carotid artery but this may not be possible. To reduce the chance of stroke, when removal of the artery is indicated it is advisable to reconstruct the artery with a vein graft from the thigh or an artificial graft. Even more extensive lesions may need an extra-intracranial bypass, which forms a conduit between the carotid artery before the blockade and the brain, which requires the involvement of the neurosurgeon. In tumours that involve both carotid arteries or in elderly patients unfit for surgery, radiotherapy is also a good treatment option; it does not cause complete disappearance of the tumour but it permanently stops the tumour from growing any further. The team of specialists required to treat complicated carotid body tumours are surgeons (head and neck, vascular and neuro), interventional radiologist, neurologist and intensivist.
Is it curable?
When removed completely the risk of the tumour coming back is almost zero. In people who live at high altitudes who have multiple tumours there is a chance of new tumours developing; this is very unlikely in those who have single isolated lesions with no familial or environmental predispositions. In people who receive radiotherapy the tumours slowly regress over time, which may be reflected as the same size on imaging; they may no shrink or ever disappear.
What does the road to recovery look like?
This depends on the extent of treatment. When a limited operation is required for a small tumour, recovery may take a few weeks. When an extensive surgery involving a carotid bypass and a brain operation, the recovery process can take much longer. When the tumour involves cranial nerves or there is dysfunction following treatment, speech, swallowing and physical therapy are a very important part of the rehabilitation plan. In spite of best practices, there is still a small risk of stroke after treatment, which requires a specialized intensive rehabilitation plan.