History
They are named after an American dermatologist, John Addison Fordyce. References
External links
DermAtlas: Fordyce spots
Fordyce spots
Differential diagnosis
Although central and obstructive sleep apnea have some signs and symptoms in common, others are present in one but absent in another, enabling differential diagnosis as between the two types:Signs and symptoms of sleep apnea generally

Signs:Observed breathing pauses during sleep
High carbon-dioxide saturation of blood, especially just before awakenings during which a patient experiences urgent need to breathe (see "Symptoms" below)
Low oxygen saturation of blood
Heart rate increase (response to both hypercapnia and hypoxemia/hypoxia), unless there also exist problems with the heart muscle itself or the autonomic nervous system severe enough to make this compensatory increase impossibleSymptoms:High frequency of urgent need to breathe upon awakening (symptom created by hypercapnia), especially among subset of awakenings occurring at times other than normal for an individuals sleep schedule and circadian rhythmsSigns and symptoms of central sleep apnea

Signs:Lack of abdominal and thoracic movement for 10 seconds or longer during sleep and coincident with breathing pausesSymptoms:Inability, either complete or without excessive effort, to voluntarily operate diaphragm and other thoracic muscles upon awakeningThe combination of this symptom with a high frequency of urgent need to breathe upon awakening is especially specific in that the co-presence of the latter symptom differentiates central sleep apneas presentation from that of sleep paralysis generally.Signs and symptoms of and conditions associated with obstructive sleep apnea
Signs:Observably ineffective respiratory movements (observable lack of air flow despite observable muscle movements indicating efforts to breathe)
Snoring (high-sensitivity but low-specificity)
Observably dry mouth or throat (high-sensitivity but low-specificity)Symptoms:Sleepiness, fatigue, or tiredness, often rising to the level of excessive daytime sleepiness
Frequent feelings of choking (airway and/or lung compression), as distinguished from mere feeling of suffocation nonspecific with respect to presence/absence of pressure, upon awakeningAssociated conditions:Opioid medication use
Large neck circumference (>16" for females, > 17" for males) (frequent causal factor and possible indirect symptom; see "Obesity" below)
Obesity (frequent causal factor and possible, albeit low-specificity, sign both direct and indirect): Obesity frequently involves accumulation of fat below the chin and around the neck, depressing the trachea when one is in the supine position, and central obesity can, depending on an individuals fat distribution, lead to increased direct pressure on the thoracic cavity and/or compressive anterior (headward) displacement of the abdominal organs, in the second case reducing space for and increasing difficulty of the motion of the diaphragm.