Neuromyelitis optica(NMO)or Devic’s syndrome is an idiopathic demyelinating disease characterized by a variable course of relapsing optic and spinal neuritis that occur conjointly or separately and interspaced with asymptomatic interludes. Although sleep disordered breathing (SDB) is an established complication of demyelinating syndromes such as multiple sclerosis (MS),there are no reports of severe OSA in cases of NMO culminating in severe polycythemia and pulmonary hypertension.
A 48-year old male was referred to the pulmonary clinic for the evaluation of a 1 year history of worsening fatigue and hypersomnolence. His Epworth sleepiness score was 18/24. He had been evaluated by his physician for similar symptoms and was noted to have a hematocrit of 67% and he was started on periodic phlebotomy. Eight years previously, he was diagnosed with NMO following a consultation for the management of variant MS that was typified by recurrent optic neuritis and global extremity motor weakness and Lhermitte’s phenomenon. He was legally blind and mildly obese (BMI; 28.4). He denied the use of alcohol or illicit drugs. Blood pressure was 130/76, pulse; 96/minute, respiratory rate; 19/minute and resting SaO2;98%.Core body temperature was normal. Physical examination revealed a middle aged male with a depressed affect. The nose exhibited mild turbinate hypertrophy and inflammation. The airway was Malampati class 3. Cardiac revealed a loud S2. Chest was clear. Neurological examination revealed bilateral optic atrophy.Power was 3+ in all extremities.There was 2+ peripheral leg edema. Abdomen was normal. Laboratory data revealed Hgb; 20.4 mg/dl, hematocrit (HCT); 59%, erythropoietin; 50 mU/ml, ABG; PH; 7.39, PCO2 52 mmHg, PO2; 66 mmHg. PFT showed the following indices of pulmonary function (expressed as percentages of predicted): FEV1; 76.5%, FVC; 69%, FEV1/FVC; 85%. TLC; 84.4%, VC; 71%, RV; 104%. MIP; 79%, MEP; 66%. DLCO corrected for Hgb was normal. Brain and cervical spine MRI showed white matter attenuation. Echocardiography showed severe right ventricle enlargement. Polysomnogram demonstrated a baseline sleep SaO2 of 85% and an SaO2 nadir of 64%. Sleep architecture was fragmented with a respiratory arousal index of 88. There was severe snoring and dysrhythmias. The apnea-hypopnea index (AHI)was 87. The average duration of apneas was 14s with a maximum of 46.5s. He was initiated on BIPAP at an IPAP pressure of 20cm H20 and EPAP of 10 cm H2O. Following 6 months of BIPAP therapy, the hematocrit normalized without repeated phlebotomy. The hypersomnolence also improved.
NMO is characterized by the preferential demyelination of the spinal cord and optic nerves and clinically unravels as a monophasic or relapsing neurological disease.The precise pathogenesis of NMO is unknown. However, NMO is considered to be a separate clinico-pathological entity from MS. SDB/OSA syndromes associated with demyelinating diseases are complex in their genesis, evolution and management owing to a complex interplay of the primary neurological pathology and socio-biological sequel to neuro-functional impairment. Inflammatory damage to the central cardiopulmonary control centers impairs the automated regulation of respiration during sleep and may cause sudden nocturnal death.In addition, myelitis mediates complex limb movement disorders that increases arousal during sleep. Moreover,the neuromuscular weakness associated with NMO impairs respiratory mechanics and augments sleep related pharyngeal hypotonia thus further reducing ventilatoty efficiency as well as mediating upper airway obstruction.These factors occur in tandem with pain syndromes,fatigue and the psychological consequences of chronic illness and thus further distorting sleep architecture.
SDB/OSA should be considered in demyelinating diseases that have fatigue and unexplained polycythemia.
Daniel Dube, None.