Narcolepsy may be mono symptomatic only ES or

Narcolepsy may be mono-symptomatic (only ES) or oligo-symptomatic (ES and cataplexy). The degree of ES is variable and the attacks of cataplexy might involve several muscle groups being triggered by emotions [1,3]. The use of modafinil in the treatment of narcolepsy is a first option for the treatment of diurnal excessive sleepiness (DES) in patients with narcolepsy. Modafinil shows several advantages when compared with the other stimulants due to smaller cardiovascular alterations and smaller risk of addiction [4]. Modafinil is a stimulant, of the non-amphetamine type, with agonist action upon the hypocretin-1 system, besides blocking the dopamine and norepinephrine transport [4]. Other indications of modafinil are for the treatment of idiopathic hypersomnia or even for residual somnolence in patients with Sleep Obstructive Apnea Syndrome (SOAS). However, there are no studies on the safety and side effects in these groups of patients [5]. Although being considered a safe drug for use in patients with narcolepsy, already being utilized for more than 20 years, modafinil presents a series of possible side effects, some of them still not fully studied and described [4].
Clinical case At the beginning of the investigation (performed in other medical facilities), a polysonogram was performed with inadequate protocol and its result led to a false negative diagnosis for SOAS. As per this negative result and the intense patient symptomatology (Epworth index of 18 at the time), we began the modafinil treatment with 100mg/day with a diagnostic glucose assay of idiopathic hyper-somnolence or even narcolepsy. The patient developed loss of muscle tonus with a consequent fall in situations of happiness or sadness, without loss of consciousness and with a maximum duration of 2 min after beginning this medication, thus characterizing a case of cataplexy. Due to the presence of this symptom and owing to the little improvement upon the sleepiness symptom, the drug dosage was increased to 200mg/day of modafinil, with additional worsening of the clinical picture. The patient demonstrated during this period an average of 12 episodes of cataplexy per day with intense social impairment. After 3 months of treatment with modafinil, the drug was discontinued with prompt resolution of the cataplexy. Polysonogram performed posteriorly with adequate protocol resulted in a severe case of SOAS. Basal polysonogram presented an index of respiratory disorder of 39.4 events/h and exam׳s minimal saturation of 64%. The test of multiple latencies of sleep (MLST) confirmed the hyper-sleepiness (average latency was 1.2min for sleep) and did not demonstrate the presence of REM sleep in any of the opportunities. We initiated a treatment with CPAP (titrated in laboratory with a pressure of 7cmH2O) with clinically marked improvement and resolution of the excessive sleepiness.
Discussion The diagnosis of SOAS is much more frequent than that of narcolepsy. We estimate that it may be over 30% in terms of prevalence of SOAS in the general population and that the one for narcolepsy is around only 0.02% [6]. However, DES is a common factor among these 2 disorders. Some clinical characteristics, such as the presence of cataplexy, age of onset of symptoms, hallucinations and sleep paralysis, do help us diagnose narcolepsy. Moreover, complementary exams such as full night sonogram, MLST, dosage of the allele HLA-DQB1⁎0602 and the level of hypocretin-1 also help us in differential diagnosing [1]. A well-done polysonogram within the recommended Brazilian Association of Sleep׳s criteria gives us the diagnosis of SOAS [7]. However, the association of the 2 diseases may happen and the initial treatment of SOAS is thus mandatory for posterior evaluation of the signs and symptoms of narcolepsy. In this described case, the patient was not initially and adequately investigated. The false-negative polysonogram and the absence of MLST were the main factors leading to the mischaracterization of a narcolepsy case.