The sudden onset of numbness, tingling, or an altered sensation on only one side of the tongue is a symptom known clinically as unilateral lingual paresthesia or hypoesthesia. Sensation in the tongue is a complex process managed primarily by several cranial nerves, including the lingual nerve—a branch of the trigeminal nerve (Cranial Nerve V)—which handles general sensation for the front two-thirds of the tongue. The glossopharyngeal nerve (Cranial Nerve IX) manages sensation and taste for the posterior third. Because these nerves run along distinct pathways, one-sided numbness can indicate a localized issue affecting a single nerve path or a more widespread neurological event. Any persistent or sudden unilateral tongue numbness requires prompt medical evaluation to determine the underlying cause.
Direct Oral and Dental Triggers
The most frequent and often least concerning cause of one-sided tongue numbness originates from injury to the lingual nerve during a dental or oral procedure. This is known as iatrogenic injury. The lingual nerve runs close to the lower wisdom teeth, making it vulnerable during extraction surgery. Injury can occur if the nerve is stretched, compressed, or directly damaged by surgical instruments or by the dental implant placement process.
A common trigger is the injection of local anesthesia during dental work, where the needle or the anesthetic solution itself can cause temporary irritation to the nerve sheath. Although most nerve injuries from dental procedures are temporary, with sensation returning within weeks to months, some cases can result in permanent loss or alteration of feeling. Symptoms often manifest as a persistent pins-and-needles feeling, a burning sensation, or a complete loss of touch on the anterior portion of the tongue on the affected side.
Localized physical trauma can also lead to temporary unilateral numbness. This includes accidentally biting the tongue severely, irritation from a sharp tooth fragment, or friction from new, ill-fitting dental appliances. Localized infections or abscesses near the base of a tooth can cause swelling that compresses the adjacent nerves, leading to a temporary sensory disturbance. Treating the source of the trauma or infection typically resolves the numbness.
Peripheral Nerve Damage and Systemic Factors
When local causes are ruled out, one-sided tongue numbness can be a manifestation of conditions affecting the peripheral nervous system or systemic health. Certain viral infections are known to target cranial nerves, causing unilateral symptoms. Herpes Zoster, the virus responsible for shingles, can reactivate and affect the Trigeminal nerve (CN V), leading to a painful, burning, or tingling sensation on one side of the face and tongue, often before a characteristic rash appears.
Another systemic factor is a deficiency in certain nutrients, particularly Vitamin B12, which is essential for maintaining the myelin sheath that protects nerve fibers. While a severe B12 deficiency usually causes a more generalized neuropathy, it can present as lingual paresthesia—a burning or tingling sensation on the tongue. This occurs because the lack of B12 impairs nerve function.
Conditions that primarily affect the facial nerve (Cranial Nerve VII), such as Bell’s Palsy, can also involve the tongue’s sensory components. Although Bell’s Palsy is defined by unilateral facial muscle weakness, the nerve branch that carries taste sensation is part of CN VII. Patients may experience an accompanying loss of taste and sometimes numbness on the affected side of the tongue. Migraine auras can also involve the tongue, causing temporary sensory disturbances that manifest as tingling or numbness. This typically lasts less than an hour and often precedes or accompanies a headache.
Central Nervous System and Vascular Events
The most urgent causes of unilateral tongue numbness originate within the central nervous system, specifically the brain or brainstem. A Transient Ischemic Attack (TIA), or a full stroke, can cause sudden-onset numbness on one side of the body, including the tongue. This occurs when blood flow to the areas of the brain that process sensory information is temporarily or permanently blocked.
These vascular events are a medical emergency, and the tongue numbness is rarely an isolated symptom. It is often accompanied by other unilateral signs, such as facial drooping, sudden weakness or paralysis in an arm or leg, confusion, or difficulty with speaking or understanding speech. Recognizing these associated symptoms is crucial, as immediate intervention is necessary to minimize potential permanent damage.
Unilateral tongue numbness can also be an early or recurring symptom of Multiple Sclerosis (MS), an autoimmune disease that damages the protective myelin sheath in the central nervous system. When MS lesions form in the brainstem, they interfere with the sensory pathways of the Trigeminal nerve, leading to altered sensation or numbness. Rarely, a tumor or other mass lesion can compress the sensory fibers, causing a progressive and persistent numbness.
Guidance on Medical Evaluation
Because unilateral tongue numbness can range from a temporary issue to a sign of a serious neurological event, seeking professional evaluation is appropriate. If the numbness appears suddenly and is accompanied by slurred speech, facial weakness, or difficulty moving a limb, emergency medical attention should be accessed immediately, as these are signs of a potential stroke or TIA.
For non-emergency situations, a consultation with a primary care provider or a dentist is the next step to identify the root cause. The diagnostic process will begin with a detailed history and physical examination, including testing the sensation and function of the cranial nerves. Depending on the suspected cause, a doctor may order specific laboratory tests, such as blood work to check for vitamin deficiencies like B12, or to screen for systemic conditions. If a central cause is suspected, imaging tests like a Magnetic Resonance Imaging (MRI) scan may be performed to visualize the brain and brainstem, looking for signs of MS lesions, tumors, or vascular damage.