Obstructive Sleep Apnea (OSA): This condition is characterized by repeated episodes of apnea or hypopnea during sleep due to upper airway obstruction, despite the presence of breathing effort. The pulse is maintained because the apnea is not due to a cardiac issue but rather an obstruction of the airway.

Central Sleep Apnea: Unlike OSA, central sleep apnea is due to a lack of breathing effort, often seen in patients with neurological disorders or those taking certain medications. The pulse remains stable as the issue is with the brain's respiratory centers, not the heart.
Seizure: Certain types of seizures, especially those originating from the temporal lobe, can cause apneic episodes. The pulse may be maintained during the seizure, especially if it's a focal seizure without significant spread to other parts of the brain.
Anxiety or Panic Attack: In severe cases, anxiety or panic attacks can lead to hyperventilation followed by apnea. The pulse, however, is typically increased due to the anxiety, but in some cases, it might remain within a relatively normal range.

Stroke: Although less common, a stroke affecting the brainstem can lead to apnea. It's crucial to identify and treat promptly to prevent further brain damage. The pulse might be maintained, especially if the stroke does not directly affect the heart or the autonomic nervous system controlling heart rate.
Myasthenia Gravis: This autoimmune disorder can cause muscle weakness, including the diaphragm, leading to apneic episodes. The pulse would likely remain stable unless there's significant respiratory failure leading to cardiac compromise.
Botulism: A rare but potentially deadly condition caused by a toxin that can lead to muscle paralysis, including the respiratory muscles, resulting in apnea. The pulse might be maintained until the condition progresses to significant respiratory failure.

Congenital Central Hypoventilation Syndrome (CCHS): A rare genetic disorder affecting the autonomic nervous system's control over breathing, leading to inadequate breathing, especially during sleep. The pulse is maintained as the issue is with the control of breathing, not cardiac function.
Prader-Willi Syndrome: A genetic disorder that can cause a variety of symptoms, including apnea due to hypoventilation. The pulse remains stable as the apnea is related to the neurological control of breathing rather than cardiac issues.