noun - A cold-stimulus headache, also known as Brain freeze, Ice cream headache or its given scientific name Sphenopalatine ganglioneuralgia (meaning "nerve pain of the sphenopalatine ganglion"), is a form of brief cranial pain or headache commonly associated with consumption (particularly quick consumption) of cold beverages or foods such as ice cream and popsicles or a dip or swim in extremely cold water.
It is caused by having something cold touch the roof of the mouth (palate), or the total immersion in water that is generally below 15°C (or 10°C or even 5°C for some acclimated open water swimmers). It is believed to result from a nerve response causing rapid constriction and swelling of blood vessels or a "referring" of pain from the roof of the mouth to the head.
Ice cream headaches result from quickly eating or drinking very cold substances while on land. It is also the result of jumping into cold water or starting an open water swim in water that is extremely cold relative to the individual. The ice cream headache can be accompanied by hyperventilating and lapses of pain, from the extremities (fingers, hands, feet and legs) to the core of the body. It can also serve as a physiological beginning of Hypothermia if the individual continues in the water without adequate training or preparation.
An ice cream headache is the direct result of the rapid cooling and rewarming of the capillaries in the sinuses. A similar but painless blood vessel response causes the face to appear "flushed" after being outside on a cold day. In both instances, the cold temperature causes the capillaries in the sinuses to constrict and then experience extreme rebound dilation as they warm up again.
In the palate, this dilation is sensed by nearby pain receptors, which then send signals back to the brain via the trigeminal nerve, one of the major nerves of the facial area. This nerve also senses facial pain, so as the neural signals are conducted the brain interprets the pain as coming from the forehead—the same "referred pain" phenomenon seen in heart attacks. Brain-freeze pain may last from a few seconds to a few minutes. Research suggests that the same vascular mechanism and nerve implicated in "brain freeze" cause the aura (sensory disturbance) and pulsatile (throbbing pain) phases of migraines.
The International Classification of Headache Disorders (ICHD) code is 13.11.2 and International Statistical Classification of Diseases and Related Health Problems ICD-10NA code is G44.8021, "Headache attributed to ingestion or inhalation of a cold stimulus".