IN DEPTH: Medical Articles And Answers To Other Questions

Neck Disorders In Little People
By Dr. George S. Bassett, M.D.

A variety of neck problems may occur in patients with dwarfing conditions because of
alterations in the anatomy of the cervical spine. The cervical spine is made up of seven
vertebrate, separated by discs (“shock absorbers”), joints, and held together by various
ligaments. The cervical spine connects the skull to the rest of the body and is constructed
so that a tremendous range of motion is possible. Each vertebrate is made up of a block of bone in front (“vertebral body”) and an arch of bone behind through which the spinal cord runs.
The spinal cord exits the bottom of the skull through a hole called the foramen
magnum and then passes through the cervical vertebra down the rest of the spine. Neck
problems may occur at three different levels of the cervical spine depending upon the
type of dwarfing condition: the foramen magnum, the upper cervical spine and the lower
cervical spine.
The growth disturbance responsible for the changes seen in achondroplasia also affects
the hole at the bottom of the skull (foramen magnum) through which a portion of the
brain and spinal cord pass. In some infants with achondroplasia, the foramen magnum
may be too small (“stenosis”). A variety of problems may occur if there is not enough
room for the brainstem and spinal cord at the level of the foramen magnum. These
include muscle weakness (“hypotonia”) or complete paralysis; breathing problems
including breath-holding (“apnea”) or blue spells (“cyanosis”); swallowing difficulties or
other feeding problems; or sudden infant death syndrome (“SIDS”). These problems
would most commonly become evident during the first two or three years of life. The
diagnosis of foramen magnum stenosis may be made by a combination of a physical
examination, electrical tests (“SSEPS”), and special X-rays (MRI). Treatment is based
upon the severity of the symptoms and findings. The foramen magnum will grow with
time so observation alone may be all that is required in most children. However, the
symptoms in some-children may be of such severity that surgical enlargement
(“decompression”) of the foramen magnum is required even at a young age. This is a
major surgical procedure and generally should not be performed unless there is
significant evidence of cord compromise.
Problems of the upper two cervical vertebrae may occur in little people of all ages with
spondyloepiphyseal dysplasia (SED), pseudoachondroplasia, chondrodysplasia punctata
(Conradi’s), metaphyseal chondrodysplasia (Schmid or McKusick types), or metatropic
dysplasia. The first cervical vertebrate (CI) is ring-shaped whereas the second vertebrate
(C2) normally has a block of bone in front shaped like a “post” (odontoid process)
projecting toward the skull around which the ring of Cl rotates. The spinal cord passes
behind this post (odontoid process) as it courses through the ring of Cl. The back half of
C2 is shaped like all other vertebrate with an arch of bone to protect the spinal cord. In
those dwarfing conditions listed above, the odontoid process may be too small allowing
for too much motion (“instability”) when the head is moved forwards or backwards. This
excessive motion may be further increased if the ligaments holding Cl and C2 together
are too loose. This is called Cl-C2 instability or atlantoaxial instability. Since the spinal cord runs behind the odontoid through the ring of CI, injury to the cord may occur if there is excessive motion. 

Symptoms of upper cervical instability may include muscle weakness, paralysis,
numbness, electrical sensations (“paresthesias”), problems with walking, loss of bowel or
bladder control, breathing difficulties, or “black-out” spells. However, many patients do
not have any symptoms associated with their cervical spine instability (“asymptomatic”).
However, these patients are at “high risk” for spinal cord injury while participating in
sports, or if they should fall or become involved in a motor vehicle accident. The
diagnosis may be confirmed by cervical spine X-rays taken with the neck in full flexion
and full extension. If too much motion is present, these two vertebrae should be
surgically fused even if there are no symptoms so that inadvertent injury to the spinal
cord does not occur. If symptoms are present, surgery must be seriously considered.
Abnormalities of the lower cervical spine often occur in diastrophic dysplasia,
campomelic dysplasia and Larsen’s syndrome. In these conditions, the neck may lose its
normal contour (“lordosis”) because of underdevelopment of the third or fourth cervical
vertebrae anteriorly. The body of the vertebrae may not be completely square in front, but
rather triangularly shaped. In addition, the normal ring of the vertebrate may be deficient
behind the spinal cord (“posteriorly”) and may be associated with loose ligaments. This
deficiency of bone anteriorly combined with loose ligaments posteriorly may allow the
involved vertebra to slide forward on the next lower normal vertebrae and create a large
angular deformity of the spine (“kyphosis”). This kyphosis may also cause injury to the
spinal cord and lead to weakness or complete paralysis. Early detection is the key and
will require a careful history and physical, as well as cervical spine X-rays. A neck brace
may be initially used in younger children with mild deformities of the cervical spine in
the hope that the deficient vertebral body will grow larger and stabilize the kyphosis
providing that there is no evidence of instability or spinal cord compromise. However,
surgical stabilization (“fusion”) is strongly advised for little people with progressive
deformities, instability, or signs of spinal cord compromise.
Dr. Bassett is an orthopedic surgeon at Children’s Hospital of Los Angeles. He is also a
member of the LPA Medical Advisory Board, and is the Medical Advisor to the DAAA.

I encourage questions from the public.  I will try to answer them as best I can.—Jenovesia

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