When One Ear Feels Blocked and Painful but the Interim MRI Shows No Change — Why Fluid Collects Behind the Eardrum, and What an Interim Scan Can and Cannot Answer

During cancer treatment, any new pain tends to be read in the most frightening way first. A sore shoulder becomes bone, an aching belly becomes bowel, a headache becomes brain. In practice, though, the source of pain is often found somewhere entirely unrelated to the tumour. A blocked, throbbing ear that feels like proof of progression may turn out to be fluid sitting behind the eardrum.

It helps to be clear about what an interim scan actually does. Imaging performed partway through treatment looks at defined areas, at a defined moment, in comparison with earlier images. A report of no change in size answers that question — it does not necessarily explain every symptom a person is feeling. If symptoms persist on the day the news is reassuring, the search for their cause continues separately. Equally, a stable scan is not a reason to dismiss a new symptom.

Fluid in the ear usually refers to otitis media with effusion, in which liquid accumulates in the middle ear space behind the eardrum. The middle ear connects to the space behind the nose through a narrow passage called the eustachian tube, which opens and closes to equalise pressure and refresh air. When the lining swells after a cold, rhinitis or sinusitis and the tube stops opening well, negative pressure develops and fluid gathers. Allergy, rapid pressure changes and acid reflux symptoms can act in the same direction.

Cancer treatment adds a few more possibilities. Radiotherapy to the head and neck region can leave the tissue around the eustachian tube swollen, or stiffer over time, so it works less well. A lesion near the space behind the nose (the nasopharynx) can press on the tube opening. During chemotherapy, mucosal injury and lowered immunity make upper respiratory infections more common, and middle ear fluid can follow. This is also why, when an adult has persistent fluid in only one ear, an ENT specialist may suggest looking directly at the space behind the nose. Being referred for that look is not in itself bad news.

A short appointment goes further when notes are prepared in advance: when the symptom started; one ear or both; whether hearing loss, ringing, dizziness or an echo of one's own voice came with it; whether there is nasal blockage, nosebleeds or a neck lump; any recent cold, flight or diving; whether there has been fever; current medicines and the date of the last chemotherapy cycle. Because fever-reducing painkillers change how a temperature reading is interpreted, note the time they were taken as well.

An ENT assessment typically includes looking at the eardrum (otoscopy), measuring how it moves (tympanometry) and a hearing test (audiometry). A thin endoscope to inspect the space behind the nose, or additional imaging, may be added when needed. What follows depends on the cause, how long it has lasted, how much hearing is affected and the current treatment schedule. Some cases settle on their own, antibiotics are not always required, and if fluid persists, placing a small ventilation tube (tympanostomy tube) in the eardrum may be discussed. During chemotherapy, the team will also check whether the timing overlaps with a period of low platelets or low neutrophils.

Some signs should not wait for the next scheduled visit: pain that worsens together with fever; sudden loss of hearing; severe dizziness with vomiting; weakness on one side of the face or difficulty closing an eye; pus or blood coming from the ear; swelling and tenderness behind the ear. Fever during the period when neutrophils are low after chemotherapy is on its own a reason to contact the treating team immediately.

The days spent waiting for results feel far longer than they are. When relief finally arrives, lingering physical symptoms are easily pushed aside. Following the cause through to an answer eases the present discomfort and also builds a record that makes the next similar symptom less destabilising. Even a brief note of when the symptom began and how it changed becomes the most useful document at the following appointment.

This article is general information and does not replace individual medical care. Causes, tests and treatment differ from person to person, so please discuss decisions with your own healthcare team.