Current understanding of tandem spinal stenosis: epidemiology, diagnosis, and surgical strategy

Overview

This review by Bai, Wang and colleagues, published in EFORT Open Reviews in 2022, summarises current knowledge of tandem spinal stenosis (TSS), the presence of stenosis in at least two separate regions of the spine (cervical, thoracic or lumbar). It is the first review to include thoracic stenosis as part of TSS. Four subtypes are described: cervico-lumbar, cervico-thoracic, thoraco-lumbar and cervico-thoraco-lumbar.

Prevalence and causes

Reported prevalence varies widely by subtype and population: radiological TSS in about 8 to 60% and symptomatic TSS in about 5 to 28% in the studies reviewed. The two main causes are degenerative spondylosis and heterotopic ossification, such as ossification of the posterior longitudinal ligament and of the ligamentum flavum. Developmental spinal stenosis, ligament ossification and stenosis in any single region increase the risk, and a low Torg-Pavlov ratio can help to identify patients at risk.

Diagnosis

Diagnosis is difficult. Upper motor neuron signs can be masked by lower motor neuron signs, and thoracic stenosis is often missed because its symptoms are nonspecific and slowly progressive. This can delay diagnosis and treatment. A thorough neurological examination along the whole spine and a high index of suspicion are advised. There are no unified radiological criteria for TSS, and none for thoracic stenosis, which limits comparison between studies.

Surgical strategy

The best approach is still debated, including how wide to decompress, whether to operate simultaneously or in stages, and in which order. Both simultaneous and staged surgery can work when patients are well selected. In cervico-lumbar TSS the region causing the dominant symptoms is usually treated first: cervical surgery first when there are upper motor neuron signs or arm symptoms, lumbar first when leg symptoms predominate. Age, comorbidities, the distance between lesions and the subtype also guide the decision, and the authors call for better trials.