68 yo WF in excellent health with prior history of intermittent benign positional vertigo for seven years and a cerebral concussion two years ago from which she recovered uneventfully in 6 weeks with no residual neurologic or physical issues.  Patient received first dose 1/19/2021 with only mild fatigue and arm soreness at injection site.   16 hours after the second dose, Patient developed a dull total cranial headache and fatigue , retiring to bed , taking no medicines. She had taken only her premarin 0.625 mg for the last week. Patient awoke at 4:30 am with severe headache, nausea and vertigo, being unable to stand without assistance.  urinary incontinence also occurred, but most likely occurred as she was unable to to get to the bathroom due to vertigo and pronounced vomiting of clear yellow fluid.  incontinence never occurred again throughout the illness. examination at this time showed nystagmus on bilateral lateral gaze and vertical nystagmus.  no other neurological signs or symptoms were present. On return to bed, Patient continued to have vertigo headache and nausea even supine with eyes closed.   Vetigo and standing instability did not respond to epley manuvers.  Headache remained mild to moderate, along with persistent vertigo and nystagmus for 4 days, becoming slightly less each day.  On the fifth day, Patient was able to ambulate unaided by holding onto walls furniture etc.  vomiting did hot reoccur after her initial bout. Headache abated on the fifth day.  Patient remained "fuzzy" and imbalanced for the next 14 days with occasional mild posterior cranial headache.  Rotary nystagmus abated on the 7th day.  Note is made that no abnormalities of the tympanic membranes were noted.  no cardiac symptoms or irregularities were noted  HR 60  BP 110/70  several attempts at epley manuvers only resulted in symptom worsening. Patient felt well enough to traveled by airplane day 8 post dose, having still some "fuzziness 'and slight imbalance, being unable to walk briskly due to gait instability..symptoms worsened slighty after air flight, and on return to home, slight barotraumatic changes were noted in the tympanic membranes, slight fluid levels and some small streaky membrane hemorrhages noted.  her gait became slighty more unstable, but she was able to walk unaided.   symptoms improved daily and by day  14 symptoms seemed to be much lessened, no nystagmus being noted.  vertigo was present only on rapidly standing , position change and vertical looking up., vertigo abating quickly after each motion at rest.  Patient traveled by plane on 3/4/21-3/8/21, vertigo escalateed to mild to moderate..no response to epley manuvers.   Vertigo worsened daily and Patient again developed mild gait instability and nystagmus bilaterally and vertically.  Ear exam was unchanged.  no headache was present during this time.   Patient was taken for balance training to a specially trained Physical therapist on 3/10/21 for evaluation , Patient being markedly symptomatic, examination showing both right and left ear abnormaities as well as vertical nystagmus.  driving was prohibited. The constellation of symptoms for the even are most consistent with acute vestibular neuronitis or central vertigo..  Neuologic localizing signs suggestive of cerebral thrombosis, etc were not present , so MRI was not performed.  Patient had Had a Notmal CT scan with here cerebral concussion two years prior.   As the symptoms weer worsening and the result of the balance training session on 3/10/21 resulted on significant worsening on awakening on 3/11/21 with moderate gait instability, bilateral horizontal and vertical nystagmus, Prednisone 40MG  po was administered.   Approximately 8 hours after the prednisone dose, Patient was able to stand unaided, and vertigo was almost totally cleared.     30mg prdnisone was administered on 3/12/21 with Patient being totally asymptomatic.  No nystagmus could be detected and epley manuvers done by the physical therapist resulted in no symptons or evoked nystagmus.  Predinsone dose was deescalated by 10 mg daily, Patient remaining totally asymptomatic.   today 3/16/21 Patient will take 5mg of prednisone, still assymptomatic, prednisone to be discontinued tomorrow.