Fornix of forebrain

Looks like

A C-shaped arching bundle of white fibres under the corpus callosum, running from each hippocampus to the hypothalamus.

What it does

The main output cable of the hippocampus, carrying memory signals to the mammillary bodies and septal area.

Keeping it well

Damage (tumour, surgery near the third ventricle) can cause severe memory loss. Surgeons take care to spare it.

Related conditions

• Acute liver failure
• ADHD
• Adjustment disorder
• African trypanosomiasis (sleeping sickness)
• Alcohol withdrawal and delirium tremens
• Altitude sickness
• Alzheimer's disease
• Amyloidosis (AL and ATTR)
• Autism spectrum disorder
• Bipolar disorder
• Birth asphyxia (hypoxic-ischaemic encephalopathy)
• Body dysmorphic disorder
• Borderline personality disorder
• Botulism
• Brain abscess
• Brain aneurysm
• Brain tumour (glioma & meningioma)
• Cerebral palsy
• Chickenpox (varicella)
• Chronic insomnia
• Chronic neuropathic pain
• Chronic pain syndrome
• Cluster headache
• Concussion (mild TBI)
• Congenital hypothyroidism
• Cryptococcal meningitis
• Delirium
• Dementia with Lewy bodies
• Dissociative disorders
• 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
• Guillain-Barré syndrome
• Haemorrhagic stroke
• Heat exhaustion & heatstroke
• Hepatic encephalopathy
• Huntington's disease
• Hydrocephalus
• Hypoglycaemia (low blood sugar)
• Intellectual disability
• Ischaemic stroke
• Japanese encephalitis
• Lead poisoning
• Long COVID (post-viral syndrome)
• Lyme disease
• Major depressive disorder
• ME/chronic fatigue syndrome
• Measles
• Medication-overuse headache
• Meningitis
• Migraine
• Multiple sclerosis
• Myasthenia gravis
• Narcolepsy
• Neurocysticercosis
• Normal pressure hydrocephalus
• Parkinson's disease
• Peripheral neuropathy
• Phenylketonuria (PKU)
• Poisoning & overdose
• Post-traumatic stress disorder
• Postnatal depression
• Postpartum psychosis
• Rabies
• Restless legs syndrome
• Roseola (sixth disease)
• Schizophrenia
• Self-harm and suicidal crisis
• Shingles (herpes zoster)
• Subdural haematoma
• Substance use disorder
• Tension-type headache
• Tetanus
• 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
• Vitamin B1, C and other deficiencies