Blood-brain barrier

Looks like

A microscopic seal formed by tightly joined cells lining the brain's capillaries.

What it does

Keeps toxins, germs and most drugs out of the brain while letting nutrients through.

Keeping it well

Breaks down in stroke, infection, tumours and multiple sclerosis; that leak is what shows up as enhancement on contrast scans.

Related conditions

• Acute liver failure
• ADHD
• African trypanosomiasis (sleeping sickness)
• Alcohol withdrawal and delirium tremens
• Altitude sickness
• Alzheimer's disease
• Autism spectrum disorder
• Bipolar disorder
• Birth asphyxia (hypoxic-ischaemic encephalopathy)
• Body dysmorphic disorder
• Brain abscess
• Brain aneurysm
• Brain tumour (glioma & meningioma)
• Cerebral palsy
• Chronic insomnia
• Chronic neuropathic pain
• Chronic pain syndrome
• Cluster headache
• Concussion (mild TBI)
• Congenital hypothyroidism
• Cryptococcal meningitis
• Delirium
• Down syndrome (trisomy 21)
• Drowning
• Eating disorders
• Encephalitis
• Epilepsy
• Essential tremor & dystonia
• Fainting (syncope)
• Febrile seizures
• Fibromyalgia
• Fragile X syndrome
• Frailty & falls in older age
• Functional (somatic) symptom disorder
• Generalised anxiety disorder
• Haemorrhagic stroke
• Heat exhaustion & heatstroke
• Hepatic encephalopathy
• High blood pressure
• High cholesterol
• Huntington's disease
• Hydrocephalus
• Hypoglycaemia (low blood sugar)
• Hypothermia & frostbite
• Intellectual disability
• Ischaemic stroke
• Japanese encephalitis
• Kawasaki disease
• Lead poisoning
• Long COVID (post-viral syndrome)
• Major depressive disorder
• ME/chronic fatigue syndrome
• Measles
• Medication-overuse headache
• Meningitis
• Metabolic syndrome
• Migraine
• Multiple sclerosis
• Narcolepsy
• Neurocysticercosis
• Normal pressure hydrocephalus
• Orthostatic hypotension & POTS
• Parkinson's disease
• Peripheral artery disease
• Phaeochromocytoma & hyperaldosteronism
• Phenylketonuria (PKU)
• Poisoning & overdose
• Post-traumatic stress disorder
• Postnatal depression
• Postpartum psychosis
• Pre-eclampsia
• Rabies
• Raynaud's phenomenon
• Roseola (sixth disease)
• Schizophrenia
• Self-harm and suicidal crisis
• Sepsis
• Shock (circulatory failure)
• Subdural haematoma
• Substance use disorder
• Tension-type headache
• Thrombotic thrombocytopenic purpura (TTP)
• Tick-borne encephalitis
• Tics and Tourette syndrome
• Toxoplasmosis & CMV
• Transient ischaemic attack
• Traumatic brain injury (moderate to severe)
• Tuberous sclerosis complex
• Vascular dementia
• Vasculitis (GCA & others)