What is the workup for a patient presenting with somnolence (excessive daytime sleepiness)?

Workup for Somnolence (Excessive Daytime Sleepiness)

The initial workup for a patient presenting with somnolence should include a two-step screening process, comprehensive laboratory testing, sleep pattern assessment using a sleep diary, and targeted screening for underlying medical conditions. 1

Initial Assessment

Step 1: Targeted Screening Questions

• Assess severity of sleepiness using validated questionnaires:
  • Epworth Sleepiness Scale (ESS) to quantify daytime sleepiness 1, 2
  • Ask "Please measure your sleepiness on a typical day" on a scale from 0-10 (scores ≥9 reliably predict abnormal ESS scores) 3

Step 2: Identify High-Risk Features

• Ask specifically about:
  • Falling asleep unintentionally during daily activities 3
  • Recent motor vehicle crashes or near-misses due to sleepiness 3
  • Sleep-disordered breathing symptoms (snoring, gasping, observed apneas) 3
  • Sudden involuntary movements of arms/legs during sleep 3

Step 3: Physical Examination

• Look for:
  • Signs of reduced salivation or scleroderma
  • Peripheral edema
  • Lower limb weakness
  • Abnormalities of gait or speech
  • Tremor
  • Blood pressure abnormalities 1

Laboratory Testing

• Essential baseline tests:
  • Complete blood count
  • Electrolytes and renal function
  • Thyroid function tests
  • Calcium levels
  • HbA1c 1
  • Ferritin levels (if Restless Leg Syndrome is suspected, levels <45-50 ng/mL indicate treatable cause) 1
  • Urine dipstick with albumin:creatinine ratio 1
  • Pregnancy test (where applicable) 1

Sleep Pattern Assessment

• Two-week sleep diary documenting:

  • Sleep quality
  • Sleep parameters (time to bed, time to sleep, awakenings, final awakening)
  • Napping patterns
  • Daytime impairment
  • Medications
  • Activities
  • Evening meal timing
  • Caffeine/alcohol consumption
  • Stress levels before bedtime 1, 3

• Sleep environment assessment:

  • Sleeping conditions (couch/bed, light/dark, quiet/noisy)
  • Room temperature
  • Presence of bed partner
  • TV/electronic device use 3

Medication Review

• Thoroughly review all medications for those that may cause somnolence:
  • Antidepressants (SSRIs, venlafaxine, duloxetine, MAOIs)
  • Stimulants (caffeine, methylphenidate, amphetamine derivatives)
  • Decongestants (pseudoephedrine, phenylephrine)
  • Narcotic analgesics (oxycodone, codeine)
  • Cardiovascular medications (β-blockers, α-receptor agents, diuretics)
  • Pulmonary medications (theophylline, albuterol)
  • Alcohol
  • Antipsychotics (especially clozapine, olanzapine, quetiapine) 3, 4

Specialized Testing

When to Consider Sleep Studies

• Refer for specialized sleep studies when:
  • Initial workup is inconclusive
  • Strong suspicion of sleep-disordered breathing
  • Treatment fails to improve symptoms
  • Suspicion of narcolepsy or other central disorders of hypersomnolence 1

Types of Sleep Studies

1. Polysomnography (PSG):

   • Indicated when there is suspicion of:
     • Sleep apnea or breathing disorders
     • Uncertain initial diagnosis
     • Treatment failure (behavioral or pharmacologic)
     • Precipitous arousals with violent behavior 3

2. Multiple Sleep Latency Test (MSLT):

   • Used to:
     • Characterize severity of daytime sleepiness
     • Identify early onset of REM sleep (characteristic of narcolepsy)
     • Should be preceded by 2 weeks of actigraphy to document sleep patterns 3

3. Actigraphy:

   • Useful for:
     • Objectively documenting sleep habits prior to MSLT
     • Assessing sleep patterns when sleep log data collection is not ideal
     • Patients with impaired cognition, literacy, or motivation 3

Common Pitfalls to Avoid

1. Overlooking medication side effects - Many commonly prescribed medications can cause somnolence 1, 4

2. Missing comorbid conditions - Depression, anxiety, and pain can significantly contribute to sleep disturbances and somnolence 1

3. Relying solely on self-reported sleep patterns - Patients with insomnia tend to underestimate sleep time; objective measures like actigraphy may be more accurate 3

4. Failing to distinguish between fatigue and sleepiness - Fatigue (low energy, physical tiredness) is more common than actual sleepiness in patients with chronic insomnia 3

5. Not assessing for high-risk driving - Patients with moderate to severe daytime sleepiness and previous motor vehicle crashes should be warned about driving risks until effective therapy is instituted 3