Head, neck & neuro for MRCS Part A

What the paper tends to test

• Questions typically test the laryngeal nerves — the external branch of the superior laryngeal nerve beside the superior thyroid artery and the recurrent laryngeal nerve beside the inferior thyroid artery — through the voice change that follows injury.
• Expect the facial nerve in the parotid: its five branches, the plane that separates the superficial from the deep lobe, and Frey’s syndrome after parotidectomy.
• Neck dissection questions ask which structures are sacrificed in a radical dissection and which nerve explains a dropped shoulder, a deviated tongue or a numb ear afterwards.
• Cranial nerve questions localise a lesion from its pattern — the cavernous sinus, the jugular foramen, the cerebellopontine angle — rather than asking for the nerve’s name.
• Extradural haemorrhage and the middle meningeal artery at the pterion, subdural haemorrhage and the bridging veins, and subarachnoid haemorrhage and berry aneurysms at the circle of Willis are examined together.
• Expect the layers of the scalp, the danger area of the face and the venous route from the face to the cavernous sinus.
• Autonomic questions test the cervical sympathetic chain and Horner’s syndrome, and the parasympathetic ganglia with the cranial nerves that carry their fibres.

Classic traps and discriminators

• The right recurrent laryngeal nerve loops under the right subclavian artery and the left under the arch of the aorta; both ascend in the tracheo-oesophageal groove close to the inferior thyroid artery. Unilateral injury gives a hoarse, weak voice; bilateral injury can give stridor and an obstructed airway after extubation.
• The external branch of the superior laryngeal nerve runs with the superior thyroid artery and supplies cricothyroid: injury flattens the voice and removes its upper range, which matters most to singers — the superior pole vessels are ligated close to the gland to avoid it.
• The hypoglossal nerve supplies all the intrinsic and extrinsic muscles of the tongue except palatoglossus (vagus); a unilateral lesion deviates the protruded tongue towards the weak side.
• The pterion overlies the anterior branch of the middle meningeal artery; a blow to the temple can fracture this thin point and cause an extradural haematoma, classically with a lucid interval before deterioration.
• Horner’s syndrome — ptosis, miosis, anhidrosis and apparent enophthalmos — follows interruption of the cervical sympathetic chain by a Pancoast tumour, a carotid dissection, a neck dissection or a stellate ganglion block, and of the T1 root in a lower brachial plexus injury.
• The spinal accessory nerve crosses the posterior triangle superficially, from the posterior border of sternocleidomastoid to the anterior border of trapezius, and is the structure most often injured in a lymph node biopsy there, leaving a dropped shoulder and weak abduction above the horizontal.

Free revision notes

Head, neck & neuro questions, answered