Chronic Solvent Encephalopathy

Chronic solvent encephalopathy is persistent neuropsychological impairment caused by long term exposure to organic solvents. It ranges from non-specific symptoms to dementia and is a diagnosis of exclusion based on exposure and cognitive testing.

Exposure. Painters, printers, degreasers, dry cleaners, shoe and leather workers, fibreglass boat builders and workers using paint strippers, thinners and adhesives. Common solvents include toluene, xylene, styrene, trichloroethylene, white spirit and mixed hydrocarbons.

Epidemiology. Occurs after many years of high exposure; the risk rises with intensity and duration, and alcohol use adds to it.

Classification. Type 1: symptoms only (fatigue, irritability, mood and memory complaint) without objective impairment. Type 2A: sustained personality or mood change. Type 2B: impaired concentration, memory and psychomotor speed on testing. Type 3: dementia.

Prognosis. Type 1 usually recovers after exposure stops. Type 2 improves partly, and type 3 is largely irreversible.

Pathophysiology.

Lipophilic solvents accumulate in the brain and disrupt neuronal membranes, neurotransmitter systems and myelin. Oxidative stress and reactive metabolites contribute.

Repeated exposure leads to diffuse white matter and cortical injury, with greatest effect on attention, memory and executive function.

• Fatigue, poor concentration, memory loss, irritability, depression, headache and sleep disturbance.
• Loss of drive and personality change in more severe forms.
• Often mild cerebellar signs, tremor and peripheral neuropathy.
• Intolerance of alcohol and symptoms worse with exposure.

Red flags.

• Rapidly progressive dementia or focal neurological signs.
• Severe depression or suicidal thoughts.
• Seizures or marked change in consciousness.

• Detailed lifetime exposure history with products, duration, ventilation and protection; alcohol and drug history.
• Neuropsychological testing across attention, memory, psychomotor speed and executive function, interpreted against premorbid ability.
• Mood and sleep assessment.
• MRI brain to exclude other disease; white matter change or atrophy may be seen but is not specific.
• Blood tests: full blood count, glucose, renal and liver function, thyroid function, vitamin B12, folate, calcium, and tests for syphilis and HIV when indicated.
• Urinary solvent metabolites show recent exposure only.

Differential diagnosis. Depression, alcohol related brain damage, primary dementia, vascular cognitive impairment, hypothyroidism, vitamin B12 deficiency, obstructive sleep apnoea, chronic fatigue syndrome, other toxic encephalopathy, head injury.

• Remove from solvent exposure; substitute solvents and improve ventilation, with respirators as an adjunct.
• Cognitive rehabilitation, sleep hygiene, graded activity and psychological support.
• Treat comorbid depression: sertraline 50 mg orally once daily, increased after at least 1 week in steps of 50 mg to 100 to 200 mg daily if needed. Maximum 200 mg daily. Review at 4 to 6 weeks and continue for 6 to 12 months after remission. Monitor sodium (especially in older adults), bleeding risk with anticoagulants or NSAIDs, suicidal thoughts in people under 25 years, and serotonin syndrome features. Use lower or less frequent dosing in hepatic impairment; no renal adjustment; acceptable in pregnancy and breastfeeding when needed.
• No drug reverses solvent induced impairment. Avoid alcohol.

Monitoring. Repeat neuropsychological testing at 6 to 12 months after exposure ends, then yearly while impairment persists.

Referral and escalation. Neurology and neuropsychology for diagnosis; occupational physician for workplace and fitness-for-work assessment; psychiatry for severe mood disorder; notification and compensation where required.

Special groups. Pregnancy: avoid solvent exposure because of foetal risk. Older adults: sertraline needs sodium monitoring.