Common ENT Investigations

 

Ear Investigations

1. Audiogram (Hearing test, Figure 1)

Indication – To assess level of hearing when hearing loss is suspected

How done – Performed in a sound-proof room. The patient is presented with sounds of different frequencies in decreasing intensities. The tester will be able to determine the level of hearing depending on the response of the patient to the different sounds. Takes about 5 to 10 minutes to do.

When Ready – Immediate

Suitability – All adults. Children as young as 4 years old may be able to cooperate and follow the instructions. The audiogram below shows bilateral high tone inner ear deafness commonly seen in age-related hearing loss.

hearing loss | audiogram

2. Auditory Brainstem Response (Brainstem-Evoked Response Audiometry)

Indication – To assess level of hearing in young infants and children. This is an objective test of hearing thresholds that doesn’t require the patient to give a response.

When Ready – Immediate although one or two days are given for the official report to be prepared.

How done – Performed in quiet room with the child sedated (Figure 2). Sometimes also done in day surgery in conjunction with other ear procedures. Electrodes are placed over the head and sound stimuli are given to the ears. Takes about 30 to 40 minutes to complete.

ENT | sedated child

Suitability – Usually done in infants and young children. Also used to confirm normal hearing in patients suspected of non-organic hearing loss (malingerers)

3. Magnetic Resonance Imaging (MRI) of Internal Acoustic Meatus (IAM)

Indication – To exclude a cerebellar pontine angle (CPA) tumor eg. acoustic neuroma, meningioma (Figure 3 yellow arrow) in patients with one-sided sensorineural hearing loss.

MRI

How done – This investigation is done at a Radiology Centre. Patients lie in a chamber which can be quite noisy and cramp. A small cannula is inserted into the hand and a dye injected. Sedation can be given to patients who are anxious or claustrophobic. The test takes about 20 to 30 minutes.

When Ready – One day

Suitability – All adults and children.

Nose Investigations

1. Postnasal Space Biopsy

Indication – To determine the nature of a suspected mass in the postnasal space (nasopharynx)

How done – In clinic under local anesthesia. The postnasal space is anesthetized with a topical anesthesia on a long cotton stick. It’s left in place for 15 minutes and a cup forceps is used to take a biopsy with the guide of an endoscope (Figure 4). Usually two or three bites are taken and the specimen sent for histological examination.

sinus | endoscopy

When Ready – Two to three days.

Suitability – All patients with a postnasal space mass.

2. Epstein-Barr Virus (EBV) Serology

Indication – Screening for nasopharyngeal carcinoma (nose cancer)

How done – This is a blood test taken in clinic. The blood specimen is sent to a lab for the test.

When Ready – Up to one week.

Suitability – All patients at higher risk of nasopharyngeal carcinoma

3. CT Scan of Sinuses

Indication – To determine extent of sinusitis as a pre-operative assessment

How done – This is done in a Radiology Centre. No dye is required and the test takes about 10 minutes.

When Ready – One day

Suitability – Adults and children suitable. Some children may require sedation if they can’t keep still.

Throat Investigations

1. Sleep Study or Polysomnogram

Indication – All snorers suspected of suffering from Obstructive Sleep Apnea (OSA)

How done – There are a few ways this test can be done. Home-based studies involve wearing a device on your arm (Watchpat 200, Figure 5) with two probes connected to the 2nd and 4th fingers. One lead is placed on the chest to measure intensity of snoring. The device is worn and turned on just before the patient goes to sleep and removed on awakening. The device is then returned to the clinic for the results to be generated. The Watchpat 200 is the latest validated sleep study tool developed so far.

sleep apnea | sleeping man

When Ready – Immediate upon returning device to clinic.

Suitability – All adults. Children generally do not require a sleep study as the cause is usually obvious eg. Large tonsils and adenoids.

Neck Investigations

1. Fine Needle Aspiration Cytology (FNAC)

Indication – Any neck lump persisting for more than one month should be subject to a needle aspiration

How done – In clinic. No local anesthesia is generally required. A small gauge needle (23F) attached to a syringe is inserted directly into the lump (Figure 6). Cells within the lump are aspirated (sucked out) from a suction effect created by withdrawing the plunge from the syringe. The aspirate is then spread onto a glass slide and sent for histological examination at a laboratory.

ENT | ump are aspirated

When Ready – Up to two days

Suitability – Adults and children suitable. Some children may require sedation if not cooperative.

2. CT Scan/ MRI Neck

Indication – To define nature of a neck lump. To stage neck disease in malignancy. CT scans examine bone structure better than MRI. MRI examines soft tissue involvement better than CT scans

How done – At a Radiology Centre. An intravenous dye may be required and injected through a small venous cannula. Takes about 20 to 30 minutes.

When Ready – One day

Suitability – Adults and children suitable. Some children may require sedation if not cooperative.

3. Ultrasound Thyroid Gland

Indication – Any persistent thyroid mass. This test will ascertain is the thyroid lump is fluid-filled (cystic), solid or mixed and whether there is any other thyroid lumps not felt on clinical examination.

How done – Usually at a radiology centre. This painless procedure involves placing an ultrasound probe over the thyroid gland and the ultrasound waves reflected from the gland is depicted on a screen for the operator to interpret. Usually takes about 15 to 20minutes.

When Ready – One day

Suitability – Adults and children suitable.

Dr Gerard Chee

MBBS (S'pore), FRCS (Edin), FRCS (Glasg) Fellow, Otology / Neurotology (Can)

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