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Fixed dilated pupil DDx

Overview

Suspect herniation due to an intracranial mass lesion as a cause of fixed dilated pupil in an unconscious patient. A fixed dilated pupil in an awake patient is NOT due to herniation.

Causes

Pharmacologic blockade is the most common cause of a fixed dilated pupil in an otherwise normal healthy patient.

A single fixed dilated (mydriatic) pupil can be caused by:

  • Pharmacological blockade– typically topical mydriatic drugs used to facilitate ophthalomological examinations.
    • anticholinergic drugs: e.g. atropine, cyclopentolate and tropicamide
    • alpha1-agonists: phenylephrine.
  • Oculomotor nerve palsy (3rd cranial nerve)
    • parasympathetic nerves are in the superficial parts of the nerve, so tend to be more vulnerable to compressivelesions and spared by vascular lesions (e.g. diabetes mellitus).
    • If an acute third nerve palsy is accompanied by pupillary mydriasis an aneurysm arising from the posterior communicating artery must be excluded.
      [See a Spider called Willis for an easy way to remember the components of the Circle of Willis and its relations.]
  • Others:
    • Holmes-Adie pupil (tonic phase)
    • post-traumatic iridocyclitis (e.g. direct facial trauma)
    • acute closed-angle glaucoma
    • physiologicalanisocoria
    • ocular prosthesis – the normal pupil may be relatively constricted due to ambient light.

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 contrastVentriculomegaly,
OTHER: Pseudofracture on X-Ray

LABS

LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia

HIGH: Bilirubin and Jaundice, HyperammonaemiaHypercalcaemia, 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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CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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