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Cervical muscle weakness is a marker of respiratory dysfunction in amyotrophic lateral sclerosis

Cervical muscle weakness in amyotrophic lateral sclerosis (ALS) indicates a poor prognosis.1 Cervical weakness has several implications, not only disturbing posture and gait, but also affecting speaking and swallowing leading to drooling, reducing respiratory and cough efficacy and impairing social interactions. Cervical orthotics can improve some of these problems.2 

Cervical muscles are important accessory muscles of respiration.3 The sternocleidomastoid is usually only recruited during greater respiratory efforts in healthy individuals, but is activated to support resting ventilation when the diaphragm is weak.3 Cervical extensor and other axial muscles can contribute to ventilation in ALS, when the diaphragm is weak.3 We have studied the association of cervical muscle strength and respiratory function in ALS.

We included consecutive ALS patients followed in our ALS clinic in Lisbon (2010–2017). Clinical assessment of flexor and extensor cervical strength was performed by one evaluator (MdC), using a standard clinical method. We recorded the revised functional ALS rating scale (ALSFRS-R) on the same day. Phrenic nerve studies and forced vital capacity (FVC) were performed within 3 months. Inclusion criteria were: definite, probable and probable laboratory-supported disease (revised El Escorial-criteria); evaluation of neck strength; disease progression. Exclusion criteria included: incomplete data; signs of dementia; severe respiratory symptoms; inability to tolerate the recumbent position; neck pain during cervical testing; associated neurological disorders; refusal of consent.

### Cervical muscle strength

Strength of neck …