Stroke refers to the sudden cessation of blood flow to the brain, causing a shutdown of the body’s limbs. The most widely known signs are slurred speech and slow movement but symptoms differ depending on which part of the brain is affected. Sometimes, the nerve controlling the tongue is damaged, which may cause changes in the appearance of the tongue.
Many people who suffer from a stroke report the more common signs, like confusion and paralysis.
Although tongue deviation is a less commonly seen sign, it has been recognised in stroke patients.
“The tongue will have a tendency to turn away from the midline when extended or protruded, and it will deviate toward the side of the lesion,” explains the journal Biomedical Engineering Online.
In other words, a crooked tongue which slants to one side or the other could be indicative of nerve damage due to stroke.
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Biomedical Engineering Online adds: “This is called tongue deviation, hence the symptoms of tongue deviation are observed in a stroke or transient ischaemic attack.”
For a long time, deviation of the tongue has been recognised as a warning sign of “wind stroke” in traditional Chinese medicine.
In a mini-stroke, also known as a transient ischaemic attack, the damage to the brain is so minor that blood supply to other areas can compensate, and a full recovery takes place.
If the hypoglossal nerve becomes damaged during a mini-stroke, however, symptoms like tongue deviation may linger.
In fact, deviation of the tongue tends to suggest that the motor cortex in the brain is damaged.
This means the hypoglossal nerve, which controls the movements of the tongue, will be defective.
In 2014, the journal Stroke described the case of a 40-year-old white man with a history of transient idiopathic thrombocytopenia, a known precursor for having a stroke.
The authors said: “Four days before his admission to our emergency room he realised he could not move his tongue to the left side while chewing bread.”
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After no reason for the symptoms could be found, the patient was referred to a neurologist for further examination.
Subsequent MRI scans revealed the left internal carotid artery had been dilated and elongated, a phenomenon medically known as dolichoectasia.
The researchers suggested the dilation may have led to compression of the hypoglossal nerve and the patient’s symptoms.
The patient had also reported difficulty swallowing, which was likely caused by the impaired motor function of the tongue.
Solitary hypoglossal nerve palsy is a relatively uncommon manifestation of stroke, with nearly half of the cases caused by cancer.
When the hypoglossal nerve – also known as the 12th cranial nerve – is damaged, this causes weakness or wasting of the tongue.
Merck Manual explains: “Hypoglossal nerve disorders can be caused by tumours, strokes, infections, injuries or amyotrophic lateral sclerosis.”
Because the hypoglossal nerve enables the tongue to move from side to side, paralysis of this nerve will cause complications when eating.