Primary Lateral Sclerosis

Primary lateral sclerosis (PLS) is a slowly progressive pure upper motor neurone disorder.

• Rare; onset at 50 to 60 years; survival is decades.

• Diagnosis requires symptoms for 4 years or more (some use 2) without lower motor neurone signs.

• About 20% convert to ALS, usually within 4 years.

• Mechanism: degeneration of corticospinal and corticobulbar tracts.

• Progressive spastic paraparesis, gait stiffness, falls, brisk reflexes, extensor plantar responses.

• Spastic dysarthria, dysphagia, emotional lability.

• Hand clumsiness; no wasting or fasciculation.

• Bladder urgency; cognitive changes in a minority.

• Clinical criteria (Pringle): isolated upper motor neurone signs, no active denervation on EMG, normal findings elsewhere.

• MRI brain and spine: possible precentral gyrus atrophy; exclude myelopathy, hereditary spastic paraplegia, MS, adrenomyeloneuropathy (very long chain fatty acids), vitamin B12 deficiency, copper deficiency, HTLV-1, syphilis, HIV.

• Repeat EMG at 12 to 24 months to detect evolution.

• Genetic testing for hereditary spastic paraplegia genes if family history.

• No disease modifying therapy; riluzole is not proven.

• Spasticity: baclofen 5 to 20 mg three times daily or intrathecal baclofen pump, tizanidine 2 to 8 mg three times daily, botulinum toxin injections, dantrolene.

• Physiotherapy, stretching, orthoses, walking aids.

• Bladder urgency: oxybutynin 5 mg twice daily. Dysphagia: speech therapy, diet modification, gastrostomy if needed.

• Pseudobulbar affect: dextromethorphan/quinidine or amitriptyline 10 to 25 mg.

• Follow up every 6 months for conversion to ALS.