Differential Diagnosis for Nocturnal Lower Extremity Immobility

• Single most likely diagnosis
  • Sleep Paralysis with Hypnagogic Hallucinations or Isolated Sleep Paralysis: This condition occurs when a patient wakes up during a sleep cycle and is unable to move, often accompanied by hallucinations. The inability to move a lower extremity could be part of the paralysis experienced during this state. It's a relatively common condition, especially in individuals with sleep disorders or those experiencing significant stress.
• Other Likely diagnoses
  • Restless Leg Syndrome (RLS): Characterized by an irresistible urge to move the legs, usually due to uncomfortable sensations. While it doesn't cause immobility, the discomfort could lead to a feeling of needing to move but being unable to due to pain or discomfort.
  • Nocturnal Leg Cramps: These are sudden, involuntary contractions of the leg muscles that occur at night. The pain from these cramps could lead a patient to feel as though they cannot move their lower extremity due to the discomfort.
  • Sleep-Related Movement Disorders: Disorders like periodic limb movement disorder (PLMD) could potentially cause a sensation of immobility or an urge to move the legs during sleep, though this is less direct.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Stroke or Transient Ischemic Attack (TIA): Although less common, waking up with an inability to move a limb could be a sign of a stroke or TIA. Immediate medical attention is crucial in these cases to prevent further brain damage.
  • Spinal Cord Injury or Compression: Acute spinal cord injuries or conditions like spinal stenosis could lead to sudden loss of mobility in the lower extremities. These conditions require urgent medical evaluation.
• Rare diagnoses
  • Narcolepsy: A neurological disorder that affects the brain’s ability to regulate sleep-wake cycles. While more commonly associated with excessive daytime sleepiness, narcolepsy can also cause sleep paralysis and cataplexy, which might be perceived as an inability to move.
  • Peripheral Neuropathy: Certain types of neuropathy, especially those affecting the lower limbs, could potentially cause significant discomfort or weakness, leading to a feeling of immobility, especially at night.
  • Psychogenic Causes: Conversion disorder or factitious disorder could manifest as an inability to move a limb without any underlying neurological cause. These are psychological conditions that require a comprehensive psychiatric evaluation.