Frontotemporal syndromes of primary lateral sclerosis

Vincenzo Silani, Barbara Poletti and Stefano Zago

in Amyotrophic Lateral Sclerosis and the Frontotemporal Dementias

Published on behalf of Oxford University Press

Published in print October 2012 | ISBN: 9780199590674
Published online November 2012 | e-ISBN: 9780191753466 | DOI:
Frontotemporal syndromes of primary lateral sclerosis

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The term primary lateral sclerosis (PLS) implies the presence of a rare motor neurone disease that causes a slowly progressive spinobulbar spasticity with weakness, eventually accompanied by dysarthria and dysphonia due to upper motor neurone disturbance. PLS is differentiated from amyotrophic lateral sclerosis (ALS) by the absence of lower motor neurone involvement, a cardinal feature of ALS (see Rosenfeld). First signalled by Türck and Charcot, it was Erb who refined the concept of ‘PLS’ to indicate a selective degeneration of the lateral columns of the cord. Ever since, long-standing sceptical discussion has arisen from the observation that many patients with PLS seemed ultimately to have different diseases such as ALS, spinal multiple sclerosis, or cervical spondylotic myelopathy.

In 1945, Stark and Moersch proposed the first clinical diagnostic criteria for PLS. These included insidious onset, slow progression, dysfunction limited to the pyramidal tracts, and a course lasting more than 5 years. Revisions of pathological observations with modern techniques and the documented presence of speech and swallowing impairments led to new established clinical and laboratory criteria. Gordon and colleagues noted that development of lower motor neurone signs inevitably follow electromyographic findings of denervation in 77% of cases within 4 years of symptom onset. They, therefore argued that a 4-year span should be a component of the diagnostic criteria, and proposed a more specific nomenclature based on the constellation of clinical and electromyographic features. In the more detailed set of diagnostic categories for the PLS-spectrum disorders, complicated PLS (PLS plus) has been considered, inclusive of predominant upper motor neurone signs plus pathological evidence of dementia. According to these revisions, at present PLS is considered to be part of the range of motor neurone diseases consisting of PLS, ALS, and progressive spinal muscular atrophy. PLS is now considered a dysfunction of the corticospinal pathway with or without very mild lower motor neurone involvement but with clinical features of prominent spasticity and pseudobulbar symptoms (dysarthria and compulsive laughing or crying). The diagnosis is usually made after the exclusion of other diseases with a similar clinical spectrum. In fact, failure to develop signs of lower motor neurone dysfunction, either clinically or electrophysiologically within 4 years of symptom onset, differentiates this entity from the more common ALS disorder. Thus, the diagnosis of PLS needs a careful clinical and laboratory investigation and an adequate follow-up. The aetiology of PLS and the genetic trait have not been identified yet, even if a family with three affected brothers has been reported and, more recently, an autosomal dominant PLS described.

Chapter.  5460 words.  Illustrated.

Subjects: Neurology

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