Bells, mono and polyneuropathies Flashcards
Bell’s palsy - definition
Idiopathic facial nerve palsy – partly a diagnosis of exclusion but features distinguishing it from other causes of facial palsy are – abrupt onset (typically overnight or after a nap) with complete unilateral facial weakness at 24-72 hours, ipsilateral numbness or pain around the ear, decrease in taste (ageusia), hypersensitivity to sounds (i.e. hyperacusis from stapedius palsy).
Features suggesting an alternative cause are – bilateral, UMN signs, other cranial neuropathies, limb weakness or a rash.
Facial nerve palsy - causes
- Most common causes are Bell’s palsy (75% of cases) or Ramsey Hunt syndrome.
- Infections – Lyme disease, meningitis (e.g. fungal), TB, viruses (HIV or polio) or mycoplasma.
- CNS – brainstem – stroke, tumour or MS or cerebellum– acoustic neuroma or meningioma.
- Systemic diseases – diabetes mellitus, sarcoidosis or Guillian-Barre syndrome (usually bilateral).
- ENT and other causes – orofacial granulamatosis, parotid tumours, cholesteatoma, otitis media, trauma to the skull base, diving (barotrauma) or intracranial hypotension.
Facial nerve palsy - symptoms and signs
- Symptoms – unilateral sagging of the mouth, drooling of saliva, food trapped between gum and cheek, speech difficulty and failure of eye closure which may cause – watery or dry eye and ectropion (sagging and turning out of lower eyelid), injury from foreign bodies or conjunctivitis.
- Signs – ask the patient to wrinkle their forehead, close their eyes forcefully and blow out their cheeks.
Facial nerve palsy - investigations
Explore other diagnoses in atypical presentations:
- MRI may show a space occupying lesion, stroke or MS.
- CSF analysis may show infection.
- Serology may reveal increased Borrelia antibodies in Lyme disease or increased VZV antibodies in Ramsey Hunt syndrome.
- Nerve conduction studies at 2 weeks can help predict recovery but they are not routinely performed.
Facial nerve palsy - management
- If given within 72 hours 60mg Prednisalone OD for 5 days improves recovery time by reducing axonal oedema and therefore damage. There is no data regarding corticosteroids given after the 72 hour window but they are widely used anyway.
- Protect the eye – dark glasses, artificial tears (e.g. hypromellose) if evidence of drying, encourage regular eyelid closure by pulling down and use tape to keep the eye closed at night.
- Surgery – if the ectropion is severe a lateral tarsorrhaphy (partial lid to lid suturing) can help but if no improvement within a year plastic surgery may be required.
Facial nerve palsy - prognosis
- Incomplete paralysis without axonal degeneration usually recovers completely within a few weeks.
- Of those with complete paralysis 80% will make a full spontaneous recovery but 20% have axonal degeneration (50% in pregnancy) so recovery is delayed and may be complicated by aberrant reconnections – synkinesis – eye blinking causes upturning of the mouth or eating causes lacrimation.
Ramsey Hunt syndrome - definition
Occurs when latent varicella zoster virus reactivates within the geniculate ganglion of the VIIth cranial nerve causing – a painful vesicular rash in the auditory canal (herpes zoster aticus) ± ear drum, pinna, tongue or hard palate.
- There is associated ipsilateral facial weakness, loss of taste, dry mouth or eyes, vertigo, tinnitus or deafness. A rare condition – incidence is 5 in 100,000.
- Diagnosis – made clinically and as early as possible as tx within 72 hours is most effective.
Ramsey Hunt syndrome - management and prognosis
- Management – 800mg aciclovir OD 5 times per day for 5-7 days and 60mg Prednisalone OD.
- Prognosis – when treated within 72 hours 75% will make a full recovery (but only 33% if not).
Mononeuropathies - definition
These are lesions of individual peripheral or cranial nerves. Causes are usually local such as trauma or entrapment e.g. by a tumour (except in carpal tunnel syndrome).
Mononeuritis multiplex
A term used if 2 or more peripheral nerves are affected when causes tend to be systemic – WARDS PLC – W – wegener’s granulomatosis, A – AIDs or amyloid, R – rheumatoid arthritis, D – diabetes, S – sarcoidosis, P – polyarteritis nodosa, L – leprosy and C – carcinomatosis.
Mononeuropathy - median nerve
C6 – T1 – nerve of precision grip – a lesion at the wrist causes weakness of abductor pollicus brevis and sensory loss over the radial 3 ½ fingers and palm.
A lesion of the anterior interosseous nerve causes weakness in flexion of the distal phalanx of the thumb and index finger.
Mononeuropathy - ulnar nerve
C7 – T1 – this nerve is vulnerable to elbow trauma – lesions cause weakness and wasting of the medial (ulnar side) wrist flexors, interossei and medial 2 lumbricals (causing a claw hand), hypothenar eminence wasting (weak little finger abduction), sensory loss over the ulnar side of the hand and flexion of 4th and 5th DIP joints is weak.
Mononeuropathy - radial nerve
C5 – T1 – this nerve opens the fist and can be damaged by compression against the humerus. Signs – test for wrist and finger drop with the elbow flexed and the arm pronated. Sensory loss is variable but the anatomical snuff box (at the root of the thumb) is most commonly affected.
Mononeuropathy - brachial plexus
Pain, paraesthesia and weakness in the affected arm in a variable distribution.
Causes – trauma, radiotherapy (e.g. for breast malignancy), prolonged wearing of a heavy rucksack, cervical rib, neuralgic amyotrophy or thoracic outlet compression (also affects the vasculature).
Mononeuropathy - phrenic nerve
C3 – C5 – palsy causes orthopnoea with raised hemi-diaphragm on chest x-ray.
Causes – lung cancer, myeloma, thymoma, cervical spondylosis, trauma, thoracic surgery, C3-C5 zoster, HIV, Lyme disease, TB, paraneoplastic syndromes, muscular dystrophy or left atrial enlargement.
