Waiting 40 years for the correct diagnosis: A complex case of comorbid narcolepsy and ADHD

To the Editor

Narcolepsy, characterized by excessive daytime sleepiness (EDS), fragmented sleep, hypnagogic hallucinations and cataplexy, is often accompanied by metabolic and neuropsychiatric comorbidities. Starting mostly before the age of 16 years, diagnosis can be difficult when typical symptoms are lacking or obscured (Reading, 2019). We present a patient with narcolepsy and attention-deficit hyperactivity disorder (ADHD) being correctly diagnosed 40 years after initial onset.

The 46-year-old Ms A was admitted due to fatigue. On admission, the main symptom was EDS. This symptom along with disturbed attention first occurred at the age of 6 years when the patient used to go to bed immediately after school, sleeping up to 14 hours/day. Since the age of 19 years, she has been experiencing recurrent action and speech arrests (1–2 minutes, being fully conscious), considered ‘dissociative’. Aged 16 years, Ms A was sexually abused and developed post-traumatic stress disorder (PTSD), including several flashbacks/year that fully remitted after a trauma therapy at the age of 42 years. Aged 25 years, ADHD was diagnosed and Methylphenidate initiated, significantly improving attention but not EDS. Aged 30 years, Ms A gained 40 kg within 12 months with no discernible cause. Six months later, she developed depressive symptoms and predominantly visual pseudohallucinations, recognizing the unreality. A schizoaffective disorder was diagnosed and treated with antipsychotics and antidepressants. While ‘schizoaffective symptoms’ remitted, weight increased by further 40 kg, both not changing after discontinuation of these drugs 6 years ago. Because of an unremarkable multiple sleep latency test (MSLT), the diagnosis of a narcolepsy was excluded 3 years ago without determining hypocretin.

On admission, body mass index was 53 kg/m². EDS was objectified using actigraphy, revealing an in-bed-time of 13 hours/day. The diagnosis of narcolepsy was confirmed by reduced cerebrospinal fluid (CSF) hypocretin levels (85 pg/mL; normal range >110 pg/mL). To pre-existing methylphenidate (30 mg twice/day), modafinil (400 mg once/day) was added, causing an almost complete remission of EDS. Therefore, both Ms A’s activity and quality of life dramatically improved.

There are several learnings from this case: first, psychiatric illnesses do not preclude neurological illnesses, yet impede their diagnosis. Here, for example, cataplexy (speech arrest) of this ‘psychiatric patient’ was misdiagnosed as ‘dissociation’ over decades. Second, an unexplained extreme weight gain, here secondary to narcolepsy, probably points to an organic cause. Third, the MSLT should be interpreted cautiously having an imperfect sensitivity in the diagnosis of narcolepsy (Trotti et al., 2013). Fourth, the combination of the psychostimulants methylphenidate and modafinil appears to be a useful option in the treatment of comorbid narcolepsy and ADHD.