title: Primary lateral sclerosis: A heterogeneous disorder composed of different subtypes?
abstract: OBJECTIVE
  To determine identifiable subgroups of patients with primary lateral sclerosis (PLS) with distinct clinical features as a first step in identifying patients likely to have the same disorder.
  
  
  METHODS
  Twenty-five patients meeting previously proposed diagnostic criteria for PLS were seen for examination, measurement of gait and finger tapping speed, and physiologic tests to assess motor pathways. Motor cortex excitability and central motor conduction time were assessed with transcranial magnetic stimulation. Brainstem motor pathways were assessed by the acoustic startle reflex. MRS was performed in a subgroup of patients to assess metabolites in the motor cortex.
  
  
  RESULTS
  Fifty-six percent of the patients with PLS had a similar pattern of symptom progression, which the authors termed ascending. In these patients spasticity began in the legs and progressed slowly and steadily. Spasticity in the arms developed 3.6 years after the legs, on average, and speech impairment followed 1.5 years later. Motor evoked potentials were absent. MRS showed a mean reduction of N-acetylaspartate/creatinine in the motor cortex. The remaining patients with PLS had heterogeneous patterns of symptom progression and physiology.
  
  
  CONCLUSIONS
  Patients with PLS with an ascending progression of symptoms form a distinct clinical subgroup that may be amenable to investigations of etiology and treatment.
authors.affiliation: Electromyography Section, National Institute of Neurological Disorders and Stroke, Clinical Center, National Institutes of Health, Bethesda, MD 20892-1404, USA.
authors.forename: P
authors.initials: P
authors.lastname: Zhai
authors.forename: F
authors.initials: F
authors.lastname: Pagan
authors.forename: J
authors.initials: J
authors.lastname: Statland
authors.forename: J A
authors.initials: JA
authors.lastname: Butman
authors.forename: M K
authors.initials: MK
authors.lastname: Floeter
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis; D001284:Atrophy; D001933:Brain Stem / Q000503:physiopathology; D002794:Choline / Q000032:analysis; D003404:Creatinine / Q000032:analysis; D018450:Disease Progression; D019054:Evoked Potentials, Motor; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000737:chemistry / Q000503:physiopathology; D016472:Motor Neuron Disease / Q000145:classification* / Q000473:pathology / Q000503:physiopathology; D009128:Muscle Spasticity; D009474:Neurons / Q000473:pathology; D011597:Psychomotor Performance; D012021:Reflex, Abnormal; D013216:Reflex, Startle
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003404:Creatinine; D002794:Choline