Numb Face and Tongue: Causes and When It Is an Emergency

A transient ischaemic attack (TIA) is an episode of stroke symptoms that resolves on its own, usually within minutes to an hour, with no lasting damage visible on tests. It creates the false impression that 'it passed and there is no problem'. In fact a TIA is a warning: it points to a focus of ischaemia and a raised risk of a full stroke in the following hours and days. Data from a systematic review show the scale of this risk and how much it depends on prompt care.

What follows from this? First, the risk of stroke after a TIA is real and concentrated in the early period. Second, a result of 0.9% versus 11.0% shows that rapid assessment and treatment in a specialist centre substantially change the outlook. That is the main reason guidelines and emergency services advise assessing sudden neurological symptoms urgently, without waiting for them to pass. These data come from observations and studies of varied method, so the pooled figure (5.2%) is an approximation, not an individual risk.

Simple scales such as FAST (face, arm, speech, time) are used to recognise stroke. In a study from Newcastle (Harbison et al., 2003), paramedics using the FAST scale made an accurate stroke diagnosis in 79% of cases (144 of 183), and the most common conditions that turned out not to be stroke were seizures, infections with confusion, cardiovascular collapse and brain tumours. A Cochrane review (2019) reminds us that prehospital scales have limited sensitivity (in the meta-analysis of ROSIER the sensitivity was 0.88, meaning about 12% of strokes and TIAs are missed) and that their results must be treated with caution. These scales rely on facial drooping, arm weakness and speech disturbance, so isolated numbness need not give a positive result. This is our editorial conclusion: the absence of obvious FAST signs does not exclude a TIA when the numbness is sudden and one-sided.

Migraine aura often includes sensory symptoms: tingling that starts in the hand, creeps up the arm and then spreads to the face and tongue on the same side. A characteristic feature is the gradual course, usually lasting from a few to several dozen minutes, often with earlier visual disturbance (shimmering lines, spots) and a headache afterwards. The phenomenon results from a wave of functional silencing of the cerebral cortex and is reversible. In stroke the symptoms usually appear suddenly and at full intensity from the start, and 'negative' symptoms (numbness, weakness) dominate rather than 'positive' ones (tingling, flashes).

This difference is helpful but not infallible. Migraine with aura can occur for the first time in older age or without a headache, and a TIA can have a mild course. That is why a first-ever episode of numbness with speech disturbance, an aura in someone over 40 to 50 who has never had migraine, symptoms different from the usual in a person with diagnosed migraine, and symptoms lasting longer than an hour all need medical assessment. We write about migraine, its types and treatment in a knowledge base entry; what matters here is that the diagnosis 'this is definitely migraine' is made for the first time by a doctor after other causes have been excluded.

One of the most common harmless causes is hyperventilation, that is, fast, deep breathing during anxiety, panic or strong stress. Blowing off too much carbon dioxide changes the pH of the blood (respiratory alkalosis), lowers the concentration of ionised calcium in the blood and increases the excitability of nerves. The result is the typical tingling or numbness around the mouth and in the fingertips of both hands, often with a feeling of tightness in the chest, dizziness and cramping of the hand muscles. What sets it apart from stroke is that it is bilateral, linked to fast breathing, and gradually eases after calming down.

Calm, slow breathing with a longer exhale helps. If the episode happened for the first time, comes with chest pain, shortness of breath unrelated to anxiety, or recurs, it is worth seeing a doctor, because such symptoms can also arise from heart or lung disease. A similar mechanism, a change in calcium concentration, applies to low blood calcium (hypocalcaemia), which causes tingling around the mouth and muscle spasms. We write about the calcium test and its interpretation in the entry on blood calcium.

Numbness of the lip, chin or half of the tongue after dental treatment is usually the effect of the local anaesthetic and wears off after a few hours. Numbness that lasts longer, for example after removal of a wisdom tooth, an implant or root canal treatment, may be injury to a branch of the trigeminal nerve (the inferior alveolar or lingual nerve) and needs prompt contact with the dentist or maxillofacial surgeon. Numbness of the chin can also be a general symptom (numb chin syndrome), which needs a doctor's assessment if there is no obvious dental cause.

Trigeminal neuralgia is above all a sudden, brief, stabbing facial pain triggered by touch, eating or tooth-brushing, not numbness as such. If, however, loss of sensation, weakness of the chewing muscles or other neurological signs dominate the picture, doctors look more often for a secondary cause (a tumour, multiple sclerosis, vascular lesions), and the EAN guideline stresses that MRI is recommended for this reason. Numbness of the forehead, eyelid and side of the nose with a blistering rash and pain suggests shingles in the first branch of the trigeminal nerve, which needs urgent antiviral treatment, especially when the eye is involved.

Tingling or itching of the mouth, tongue and throat within minutes of eating a raw fruit or vegetable (apple, peach, carrot, nuts) in someone allergic to pollen is typical oral allergy syndrome (OAS). It is usually mild and passes within a dozen or so minutes, and we write about its mechanism and cross-allergy in a separate article. A completely different situation is increasing swelling of the tongue or lips, hives, shortness of breath, wheezing, vomiting or dizziness after a meal or a drug: that is anaphylactic shock, which needs adrenaline and an immediate call to emergency services.

Vitamin B12 deficiency leads to damage of the peripheral nerves, but can also cause inflammation of the tongue (a red, smooth, burning tongue) and paraesthesia. Although facial numbness is rarer than numbness of the feet and hands, when it comes with fatigue, tingling of the limbs or risk factors (a plant-based diet, metformin, proton pump inhibitors), a B12 test is justified, and we write about its interpretation in the vitamin B12 entry. In young adults, especially women, numbness of half of the face that builds over days and lasts for weeks can be the first attack of multiple sclerosis and needs assessment by a neurologist with MRI.

Rarer causes include reactions to drugs and substances (some antibiotics, cancer drugs, abused nitrous oxide), diabetes, infections, tumours of the cerebellopontine angle or skull base, and inflammation of the facial nerve (Bell's palsy), in which drooping of the whole half of the face including the forehead dominates rather than isolated numbness. Burning tongue without any change in the mucosa, more common in women after menopause, is burning mouth syndrome, distinct from numbness. A separate and harmless curiosity is numbness of the tongue and lips after Sichuan pepper or very hot food, which passes within a few dozen minutes.

Numbness of the face and tongue is one of the symptoms where the value of the information depends on the pace. The safest rule is asymmetrical: sudden and one-sided we treat as an emergency, even if it has passed, while gradual, bilateral or clearly tied to a circumstance (anxiety, the dentist, food) can first be sorted out and discussed with a doctor in the usual way. The cost of an unnecessary call to 112 is negligible compared with the cost of a missed stroke.