Cranial nerve lesions DDx

Overview

Differential diagnosis of cranial nerve lesions includes central and peripheral causes. Causes vary according to which cranial nerve is affected, and whether multiple cranial nerves are involved. See also Bulbar and pseudobulbar palsy

Causes

Multiple cranial nerve lesions

• nasopharyngeal CA
• chronic meningits (e.g. CA, hematological malignancy, TB, sarcoidosis)
• GBS (motor only)
• Brainstem lesions (esp vascular with crossed long tract signs, tumors)
• Arnold-Chiari malformation
• Trauma
• Paget’s disease of bone
• Mononeuritis multiplex e.g. DM

Cranial nerve III

Common

• idiopathic
• trauma

Central

• brainstem vascular lesions
• tumor
• demyelination

Peripheral

• compressive lesions, such as PCOM aneurysm tumour, basal meningitis, nasopharyngeal carcinoma or orbital lesions
• ischaemia or infarction, as in arteritis, diabetes mellitus and migraine.

Features

• complete ptosis (partial ptosis may occur with an incomplete lesion)
• divergent strabismus (eye ‘down and out’)
• dilated pupil
• unreactive to direct light (the consensual reaction in the opposite normal eye is intact)
• unreactive to accommodation.

Q. How can a CN4 palsy be ruled out in a patient with CN3 palsy?

• Always try to exclude a fourth (trochlear) nerve lesion when a third nerve lesion is present.
• Tilt the head to the same side as the lesion.
• The affected eye will intort if the fourth nerve is intact (remember SIN-the superior oblique intorts the eye).

Cranial nerve IV

rare!

• idiopathic
• trauma
• lesions of the cerebral peduncle

Features

• Failure to intort the eye
• The patient may walk around with his or her head tilted away from the lesion – that is, to the opposite shoulder (this allows the patient to maintain binocular vision)

Cranial nerve VI

Bilateral lesions

• trauma
• Wernicke encephalopathy
• Mononeuritis multiplex
• raised ICP

Unilateral lesions

• idiopathic
• trauma
• central (e.g. vascular lesion or tumour)
• peripheral (e.g. raised intracranial pressure or diabetes mellitus)

Features

• failure of lateral movement
• convergent strabismus
• diplopia.
• signs are maximal on looking to the affected side, and the images are horizontal and parallel to each other.
• the outermost image from the affected eye disappears on covering this eye (this image is usually also more blurred).

Cranial nerve IX and X

Central

• vascular lesions (e.g. lateral medullary infarction, due to vertebral or posterior inferior cerebellar artery)
• tumours
• syringobulbia
• motor neurone disease

Peripheral (posterior fossa) lesions

• aneurysms at the base of the skull
• tumours
• chronic meningitis
• Guillain-Barré syndrome

Q. Which way is the uvula drawn in a unilateral CN X palsy?

• towards the normal side

Cranial nerve XI

Unilateral

• trauma involving the neck or the base of the skull
• poliomyelitis
• basilar invagination (platybasia)
• syringomyelia
• tumours near the jugular foramen

Bilateral causes

• motor neurone disease
• poliomyelitis
• Guillain-Barré syndrome.

Note: bilateral palsy may mimic muscular dystrophy (esp dystrophia myotonica)

Cranial nerve XII

Bilateral UMN

• vascular lesions
• motor neurone disease
• tumours, such as metastases to the base of the skull.

Unilateral LMN

Central

• vascular lesions, such as thrombosis of the vertebral artery
• motor neurone disease
• syringobulbia.

Peripheral

• posterior fossa: aneurysms or tumours, chronic meningitis and trauma
• in the upper neck: tumours or lymphadenopathy
• Arnold-Chiari malformation.

Bilateral LMN lesions

• motor neurone disease
• Guillain-Barré syndrome
• poliomyelitis
• Arnold-Chiari malformation.

Q. Why is there usually no deviation of the tongue with a unilateral UMN lesion of CN12?

• The tongue, like the face (CN7) and palate (CN10), has a bilateral UMN innervation in most people

CCC Differential Diagnosis Series
NEURO	Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision
RESP	Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement
CVS	Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction
GIT	Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage
GUT	Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency,
MSK	Arthritis, Shoulder pain, Wasting of the small muscles of the hand
DERM	Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans
ENDO	Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss
HAEM	Splenomegaly
PAEDS	Floppy infant
MISC	Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest
IMAGING	CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR, ABDO: Gas on abdominal X-ray, Kidney mass, BRAIN: Intracranial calcification, Intracranial structures with contrast, Ventriculomegaly, OTHER: Pseudofracture on X-Ray,
LABS	LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia,  HIGH: Bilirubin and Jaundice, Hyperammonaemia, Hypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia,  ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis, Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes

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