Progressive narcolepsy: how to deal with intermediate hypocretin-1 values?

Area of Science:

• Neurology
• Sleep Medicine
• Neurochemistry

Background:

• Narcolepsy type 1 diagnosis relies on clinical symptoms and hypocretin-1 levels, with a threshold of <110 pg/mL in cerebrospinal fluid (CSF).
• The established CSF hypocretin-1 threshold for narcolepsy type 1 diagnosis is debated, with proposals for alternative values in the intermediate range (110-200 pg/mL).

Observation:

• A patient presented with classic narcolepsy type 1 symptoms over six years, but initial tests showed normal polysomnography, a normal multiple sleep latency test (MSLT), and intermediate CSF hypocretin-1 (132 pg/mL).
• Four years later, the patient's CSF hypocretin-1 dramatically decreased (<50 pg/mL), and MSLT became abnormal, confirming the narcolepsy type 1 diagnosis.

Findings:

• This case demonstrates that initial intermediate CSF hypocretin-1 levels do not exclude narcolepsy type 1.
• A significant decrease in CSF hypocretin-1 over time can aid in confirming the diagnosis.

Implications:

• Reassessment of CSF hypocretin-1 is vital for patients initially presenting with intermediate values.
• This case contributes to the ongoing discussion regarding optimal CSF hypocretin-1 thresholds for narcolepsy type 1 diagnosis.