Carol is a 62 year old female who has had episodes of dizzy spells and associated nausea over the last few weeks. She explains that episodes usually occur upon waking as she rolls over and sits up in bed. She immediately feels ‘the world is spinning’ around her for approximately a minute before symptoms spontaneously resolve. Carol denies any hearing loss, tinnitus or headaches.
Systems examination including neurological examination is intact. Dix-Hallpike manoeuvre provokes a clockwise torsional nystagmus and vertigo lasting approximately 45seconds.
What is the most likely diagnosis?