Larynx and hypopharynx anatomy & pathology Flashcards
Anatomy Summary
Larynx anatomy
Suprahyoid larynx
Bottom images - false cords
False cords contain some fat
Will see some of the cartilage of arytenoids at level of false cords in supraglottis
Glottic larynx
You should see cricoarythenoid joint and thyroid cartilage at level of true vocal cords (See first image)
Subglottic larynx
- Look for signet ring of cricoid
- SHOULDNT see arythenoid cartilages
Will see cricothyroid joint on either side (blue asterisk)
Thyroid cartilage
Ossifies with age
Thyroid cartilage will all be low on ADC
- Ossification can be asymmetric
- Irregular ossification is normal
- Bottom ossifies first, then top then middle
Extrinsic ligaments of the cartilages
Intrinsic muscles of larynx
Thyroarytenoid muscle in red Supraglottis
Bulk of thyroarytemoid muscle (red) and Inter-arytenoid muscles - purple
posterior crycoarytenoid muscle - green Subglottis
TNM Staging of Laryngeal cancers
What to comment on?
x
Best CT phase for imaging tumours of neck?
Late venous phase CT
NOT arterial
Apperance of tumours of MRI?
Low T2 (grey signal)
Post contrast T1 - tumour will enhance less than surrounding peritumoural oedema
Pre-epiglottic space involvement in supra- glottic cancers
Need to mention if invasion as dictates T grading.
On CT anterior aspect of epiglottis can appear slightly hyperdense (this is normal)
Use MR to determine if invasion.
Invasion of para-glottic space
How to determine invasion?
Look for obliteration of fat.
Beware invasion of POSTERIOR paraglottic space - can easily spread to hypopharynx.
Involvement of paraglottic space can facilitate spread across trans glottic planes
White is just oedema. Not involvement
Glottic cancers
Tumour of vocal cord - where do they usually spread?
CT can miss small tumours. MRI better.
Tumours of true vocal cord tend to spread anteriorly to commisure and then across to other side.
Can also spread downwards.
Look out for nodularity of cricoid ring in the hypopharynx - can be a sign of inferior tumour spread from glottis. (subglottic spread)
Hypopharynx cancers
What is significance of pyriform sinus apex involvement?
Pyriform cancers spread circumferentially and can extend into soft tissues.
The apex is most inferior point near the level of glottis. Near the oesophagus on the left side so important to comment on involvement.
Post cricoid vs posterior hypopharyngeal wall cancer
Identify post circoid area. Look for thin line posterior to cricoid - which represents hypopharynx lumen.
If lesion is anterior to the line it is post cricoid.
If lesion is posterior hypopharyngeal wall is behind this.
Post hypopharyngeal wall cancer is more common (post cricoid rare). Spreads up and down and usually arises higher in hypopharynx.
- Look for pharyngeal contrictor muscles when there is a hypopharyngeal muscle.
- Is prevertebral muscles and fascia involved? Look at DWI to determine involvement.
- Look for LN mets - 75 of cases of hypopharyngeal cancer have at presentation.
How to detect laryngeal cartilage invasion?
- Sclerosis (sensitive but not specific for invasion. can be overcalled)
- Erosion (Specific)
- Extra-laryngeal spread (specific)
Erosion is a late sign.
Beware of inflammation vs tumour when assessing cartilage
Picture represents tumour involvement of cricoid
Note low T2 signal and hypoenhancement relative to oedema
Can look eroded or involved on CT but important to correlate MRI apperance as may be normal. Could be unossified cartilage rather than erosion (see first image).
Perineural spread through superior laryngeal nerve
Where is tumour access to nerve?
Through thyroid foramen. At posterior aspect of thyroid cartilage.
Provides direct access into soft tissue and nerve.
Beware of in glottic cancers.
Tumour extending through foramen.
Where can chondroid tumours occur in neck?
Chondroid lesions dont cause diffusion restriction.
Think of in a lesion of the cricoid with high T2, irregular enhancement and high ADC.
How to identify level of true vocal cords?
Arytenoids are oriented at 45 degrees. The cricoid is seen.
Laryngocele and tumour
Where does laryngocele arise from?
Arises from laryngeal ventricle and can extend superiorly.
This is a large cystic lesion.
Three laryngocele subtypes are described 2:
- internal (or simple): the dilated ventricular saccule is confined to the paralaryngeal space; it is contained by the thyrohyoid membrane (~40%)
- external: the saccule herniates through the thyrohyoid membrane, and the superficial portion is dilated (~25%)
- mixed: with dilated internal and external components (~45%)
Tumour can grow in laryngocele. How to look for this??
- Look for post contrast enhancing tissue and low ADC to determine tumour.
- If not tumour present they may watch laryngocele or remove if causing mass effect.
Measuring ADC value in tumours of H&N
Usual ADC of SCC is around 1.
If lower than this/ very low ADC - consider lymphoma.
How to determine if a mass arises in the pyriform sinus or not?
Look for the aryepiglotic fold - if it is displaced anteriorly then it is in pyriform sinus.
If aryepiglottic fold is displaced posteriorly then originates anterior to this.
