Vertigo causes a feeling of dizziness or spinning even when one is stationary. It may be accompanied by nausea or vomiting. The inner ear contains a maze of loops and pouches called the semi-circular canals and otolithic organs. Combined this makes up the vestibular system. The semi-circular canals contain fluid and are located at right angles to each other. When we change position the movement of the fluid in these canals sends messages to the brain, which, combined with input from the eyes, gives us our sense of position and balance.
Benign positional vertigo (BPV) causes sudden brief episodes of dizziness that characteristically occur with changes in position of the head. It is most common in those over 60, which makes it the most likely cause for your mother, but it can occur in other age groups. There are small crystals that normally lie in the otolithic organs. In BPV, some of these may be dislodged, moving into the semi-circular canals. This alters the message to the brain, leading to the symptom of dizziness.
Medication is usually prescribed. Another treatment involves a series of head movements performed by a specialist (this is called the Epley manoeuvre), which allow the crystals to reposition allowing nerve messages to fire correctly again. Exercises are often given to improve core stability. This is often worth trying as it can really help in some people.
You are correct in saying that the medication prescribed can make some people sleepy. This can be an intolerable side effect for some. The major complication of BPV is falls due to unsteadiness. Falls in the elderly can have serious consequences such as bony breaks, so you are right to be concerned.
Vestibular neuritis causes sudden onset of severe vertigo that can persists