Neurological symptoms complicating the paroxysmal coughing associated with cystic fibrosis were studied in 273 patients, aged 10 to 44 years, attending the Cystic Fibrosis Research Center, Divisions of Pediatric Pulmonology and Neurology, Case Western Reserve University School of Medicine and Rainbow and Children’s Hospital, Cleveland, OH. Lightheadedness in 47% and headache in 50% of those with paroxysms were the most common neurological symptoms. Confusion, visual loss or dimming, paresthesias, speech disturbance, tremors, paralyses of extremities and face, and syncope were less frequent, transient abnormalities. The pathophysiology of these symptoms was explained by high intrathoracic pressure, as in cough syncope, that is transmitted to the cerebrospinal fluid, compressing cranial vessels and resulting in a “bloodless brain“ or transient cerebral ischemia. In some patients with headache, marked hypoxemia and hypercapnia accompanied the coughing paroxysm and aggravated the symptom, but in most this mechanism was unlikely, and irreversible sequelae were not observed. 
COMMENT. Unlike pertussis, in which paroxysmal coughing, episodic apnea and cyanosis, or disturbed ventilatory perfusion may result in severe hypoxemia and neurological dysfunction, the coughing in cystic fibrosis is rarely accompanied by significant hypoxemia and serious neurological sequelae. A direct effect of B pertussis toxins on surfactant function leading to alveolar atelectasis has been invoked as the cause of hypoxemia in pertussis.