Surgical anatomy of the neck

===Lecture Details===
Jonathan Serpell
===Lecture Content===
Thyroid is bilobed shield, enlargement is goitre, can be solitary, multiple nodules or diffuse enlargement. Questions to ask are is whole gland enlarged or just solitary nodule, whole gland is it diffuse or uniform.
Pemberton's sign is large goitre crossing thoracic inlet extending retro-sternally into chest, when arms are elevated diameter of this inlet reduced and blocks venous return causing patient to go blue. 
Exopthalmos is common in Graves' disease. Thyroid is overlaid by sternomastoid with deep investing fascia, below that are strap muscles omohyoid and sternohyoid, below that is sternothyroid. Below that is thyroid, very vascular (superior thyroid with recurrent laryngeal). Venous drainage is to brachiocephalic vein. Parathyroids are posterior. L recurrent laryngeal loops around the aorta. Right can go around aorta or be non-recurrent (0.5% of population). Recurrent n is branch of vagus, is motor to intrinsic muscle of laryx except cricothyroid. Sensory is for larynx below vocal cords, course is tracheo-oesophageal groove. 
Visceral layer can slide across prevertebral (orange) fascia. Pyramidal lobe is embryological remnant from foramen cecum. Inferior parathyroid has more variable position due to embryological derivatives. Superior PT is above recurrent nerve, inferior tends to be anterior to this.
During thyroidectomy external laryngeal nerve is at risk which tenses the vocal cord, at risk during ligation of vessels, may cause weaker voice, not able to sing. Recurrent laryngeal nerve unilateral dissection causes hoarse voice, both can cause airway obstruction and potentially tracheostomy. PTH can cause hypocalcaemia.
Haemorrhage can be bleeding beneath deep cervival fascia and strap muscle layer, can cause increased pressure as it is a confined space, can stop lymphatic and venous drainage causing airway obstruction and death if not removed. Requires opening wound, skin and deep fascia to release pressure.
Pre-auricular or retro-mandibular salivary card, 100% serous, divided into superficial and deep lobes by plane of facial nerve, contains superficial to deel facial nerve, retromandibular vein, external carotid artery, lymph nodes. Parotid duct opens above second upper molar tooth. 
Branches of facial nerve are pes anserinus (crow's foot). Complete palsy can cause keratitis and corneal ulceration due to drying of schlera. Parotid problems can be in both glands (mumps), tumour within gland can be treated with surgery, preserve facial nerve, usually superficial. Stones are uncommon, other infection envelop dense parotid fascia, swelling increases pressure causing pain.
Submandibular glands are in digastric triangle, U shaped gland passing around posterior of mylohyoid divides it into superficial or deep lobes, mixed serous 70% and mucus. Superficial has marginal mandibular branch of the facial nerve. Deep is part of lingual nerve. Can have stones, infections or tumours (from most common to least).
Sublingual gland also exists. Digastric triangle is overlapped by stylohyoid. Hyoid to tongue is hyoglossus. There is also styloglossus, genial tubercule on mandible has genioglossus, geniohyloid. Midline raphe of mylohyoid is inferior 'diaphragm' of the tongue. Submandibular duct opens in floor of the mouth beside the frenulum. Runs over the sublingual gland. Lingual nerve gives inferior alveolar. Lingual can be at risk during submandibular stone removal as it loops over the submandibular salivary duct. Hypoglossal nerve is quite a bit lower down.
Stone in duct- anterior floor of mouth, beware of injury to the lingual nerve, tumour or stone in posterior gland requires removal of the whole gland, beware marginal mandibular branch of the facial nerve and the lingual nerve as it is a superficial relationship running over the gland.
Wry mouth is due to marginal mandibular being damaged, supplies depressor ori, is mouth hanging down. There are about 200-400 arranged into groups, drain lymphatic fluid from cancers and infections. Site and features of nodes may indicate site of problem and nature of pathology. There is an outer circular group (submental, submandibular, post-auricular, occipital), drain into upper deep cervical nodes. Inner circular (adenoids, lingual tonsils) drain into deep cervical. Deep vertical drain along internal jugular, deep vertical drain to deep cervical nodes. Deep cervical are divided to upper, middle and lower. Deep cervical drain into jugular lymph trunks.
Jugulo-digastric lymph node is upper deep cervical node, drains from palatine tonsil, classic node enlarged with a sore throat, often permanently enlarged in children. Is at junction of jugular vein and digastric muscle. Jugulo-omohyoid node is a bit lower down, drains from the tongue. 
Virchow's node is left inferior deep cervical node, drains head and neck and also some from chest and abdomen, can be enlarged eg in pancreatic cancer. Enlargement is Tousierre's sign.
Posterior triangle nodes run with accessory nerve (nodes are deep to this), accessory nerve is in roof of posterior triangle just under deep cervical fascia therefore relatively superficial and can be at risk, at risk in lymph node biopsy and results in shoulder weakness and shoulder drop.
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