L1 Syndrome and the Thumb

L1 Syndrome is a rare condition that primarily affects the nervous system including the brain but also the nerves to the arms and legs.  The name L1 syndrome comes from the name of the altered L1CAM gene.  Alterations in this gene affect the L1 protein which then affects nervous system development.  L1 Syndrome is passed to children through the X chromosome (X- linked recessive transmission).  Because boys only have 1 X chromosome- if they get this particular X chromosome, they will have L1 Syndrome and so it is more likely in boys.  A girl has 2 X chromosomes and so would need both X chromosomes (one from each parent) to be altered- much less likely.  http://www.ncbi.nlm.nih.gov/pubmed/20301657  and http://ghr.nlm.nih.gov/condition/l1-syndrome .  

Most of the abnormalities of L1 Syndrome are not related to my field of hand and upper extremity surgery.  Each child is unique but there are a series of differences that are commonly seen.  These include hydrocephalus (too much fluid around the brain), mental retardation, delayed speech, and spasticity.  The spastic paraplegia may require a wheelchair but also presents with a shuffling walk.  Like most syndromes, the severity of any one of these problems is different for each child.

The most common hand issue in L1 Syndrome is the adducted thumb- it is the reason for referral to the hand surgeon.  Adduction of the thumb is a position in which the thumb is pulled towards the index (pointer) finger.  The thumb can also be flexed (bent).  This position of the thumb is a problem for 2 reasons.  First, the thumb can be in the way of finger motion (preventing finger flexion). Second, the thumb position simply prevents the thumb from acting like a thumb (i.e., grabbing large objects).   

In the patient below, another issue is the position of the fingers- they are deviated away from the thumb, a so- called wind- swept or wind- blown hand.  This is an uncommon problem also; I most commonly see this in patients with  http://ghr.nlm.nih.gov/condition/freeman-sheldon-syndrome .  This combination of thumb adduction and finger position can also be a type of arthrogryposis (Distal).    

Other conditions can be associated with a flexed/ adducted thumb posture including cerebral palsy (CP) and congenital clasped thumb.  These conditions are each quite different.  CP may respond to splinting and stretching but often surgery to let the thenar (thumb) muscles slide with an EPL tendon reroutement (moving the tendon makes the tendon a abductor of the thumb rather than an adductor) will help.  Congenital clasped thumb (present at birth) may get better with age and splinting but also occasionally requires surgery also.  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2656739/

L1 syndrome patient, left hand.  Note the position of the thumb (somewhat hidden) and fingers around the wheelchair wheel.

The thumb in L1 syndrome. The right hand is more mildly affected here but cannot be straightened or positioned differently.

L1 syndrome.  Left hand x-rays.  The thumb is close to the fingers but the most impressive finding is the position of the fingers.  They are deviated away from the thumb, a "windswept" hand.

Patient with L1 syndrome.  Note his hand position.

In this patient, we will plan to address the thumb with surgery (he has been splinted and in therapy for years).  Hopefully, repositioning the thumb will allow improved overall function.