Double Crush Syndrome

Introduction

• The double crush hypothesis was first formulated in 1973 and states that axons that have been compressed at one site become especially susceptible to damage at another site.
  
• This theory was originally described by Upton (1973) in a study of 115 patients.
• The existence of double crush syndrome was further substantiated by Massey's (1981) study of nineteen cases of carpal tunnel syndrome co-existing with a cervical radiculopathy. 
  

Hypothesis

• It is suggested that compression of an axon at one location makes it more sensitive to effects of compression in another location,because of impaired axoplasmic flow.
• Hypothetically, two lesions with little or no independent clinical ramifications, when combined, lead to appearance or magnification of symptoms
• Two areas of compression affecting the same axons do not, alone, meet the criteria of the hypothesis.
• By definition, a first lesion must render axons more susceptible to effects of a second, leading to more than just the combined, independent effects of two lesions
• Upton and McComas [1] used the double
  crush hypothesis to explain why patients with carpal tun-nel syndrome (CTS) sometimes feel pain in the forearm,
  elbow, upper arm, shoulder, chest, and upper back. They
  also used it to explain failed attempts at surgical repairs
  when neither surgery nor CTS diagnosis appeared faulty.
  They claimed that most patients with CTS not only have
  compressive lesions at the wrist, but also show evidence of
  damage to cervical nerve roots.