Persistent Early-morning Headache: What's Your Dx?

A man in his mid-40s presents to the emergency department (ED) at 4 am complaining of intermittent nighttime headaches of 2 weeks’ duration; the pain often wakens him at about 3 am. He had been to the ED 2 weeks earlier with similar symptoms concerned that he had the avian flu because one of his pet canaries had died. Results of evaluation at that time, including routine blood work, a CT of the head and a lumbar puncture, were all unremarkable, so he had been discharged home with a recommendation to see his PCP.

He returns to the ED today claiming that his left arm has been numb for 45 minutes. He denies weakness or chest pain but says the headache has been ongoing and that he had 2 episodes of vomiting earlier that evening. His vital signs and physical examination are all entirely normal.

He mentions that he saw a chiropractor just after New Year’ Day (about 2 weeks ago) and had neck manipulation so a CT angiogram of the neck was performed and was negative for vascular dissection. His CBC is remarkable for a hemoglobin of 20 g/dL, but the WBC and platelet counts are both normal (making polycythemia vera unlikely). Blood chemistries also are normal. He does not appear clinically dehydrated so hemoconcentration is not likely to be the cause of the elevated hemoglobin.

During observations you notice that his pulse oximetry is normal while he is awake, but drops to the low 90s when the patient falls asleep. Suspecting chronic hypoxia and/or sleep apnea as a cause of his high hemoglobin you consider ordering an arterial blood gas (ABG).

-- Would the results likely be helpful? 

-- What finding might explain night-time headaches and possible polycythemia as well?

-- What's your diagnosis?

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