Lambdoid Synostosis Facts
The lambdoid suture is located on the back of the skull and extends from the midline and to an area behind the ears. Lambdoid suture synostosis is the least common type of single suture synostosis. Premature closure leads to flattening of the back of the head on the affected side and is known as plagiocephaly. It can be easily confused with positional plagiocephaly which is caused by the baby sleeping preferentially to one side. The latter does not need surgery and is treated with physical therapy and helmets. Lambdoid suture synostosis can lead to marked changes in the baby's skull base. The affected mastoid area is displaced downward and the cranial vault can lean sideways.
The lambdoid suture is located in the back of the skull as seen on this newborn's skull and marked with red.
Both lambdoid sutures, marked in red, as seen on the back of a newborn's skull.
Back view of an adult skull showing the location of both lambdoid sutures (red lines) as the extend from the mastoid bones to the sagittal suture (black lines) on the top of the skull.
Presentation
The classical presentation consists of flattening and depression of the back of the head on the affected side. When viewed from above, the shape can have a trapezoid shape (Figures 1,2,3 ).When viewed from the back, the affected sides shows the mastoid and ear to be displaced downward in relation to the non affected side (Figures 4,5,6). The head tends to tilt sideways, producing cranial scoliosis (Figures 7,8,9 ). Care must be taken not to confuse the head shape with the common deformation caused by positional molding caused by the anti SIDS program of sleeping on the back (Figure ).
Figure 1. Head shape as seen from above in a patient with left lambdoid synostosis shows flattening of the left side of the head.
Figure 2. Top view of 6 month old male with left lambdoid synostosis showing a similar head shape.
Figure 3. This 8 month old girl presented with right lambdoid synostosis. The asymmetry of the back of the head is evident as marked compensatory growth has taken place on the left side.
Figure 4. Back of the head view of an infant male with left lambdoid synostosis shows downward displacement of the left mastoid process (red dot) compared with the unaffected right mastoid process (green dot).
Figure 5. Seven month old male with right lambdoid synostosis shows downward displacement of right ear in relation to the left ear.
Figure 6. Intra-operative markings show skull base line (A) and inferior displacement of left mastoid bone (red dot) and normally placed right mastoid bone (Green dot) in a patient with left lambdoid synostosis.
Figure 7. Ten month old male with right lambdoid suture closure shows deviation of the top of the head toward the opposite side.
Figure 8. Cranial deviation caused by right lambdoid craniosynostosis. Red line shows axis of the cranium and the black line the axis of the skull base.
Figure 9. Line A shows the axis of the top of the head and the deviation of the axis of the skull base (B) leading to scoliosis of the cranium. Normally it should be a straight line from top to bottom.
Radiology
Unlike other single suture synostosis, radiologic studies are needed to assure that the correct diagnosis is made. Because it can be easily confused with positional molding, X-rays or CT scans are very useful in helping make the diagnosis.
Figure 10. 3-D CT scan of patient with partial closure of the left lambdoid suture near the midline sagittal suture.(Black arrows)
Figure 11. 3-D CT scan of infant with an area of "spot welding" in the middle of the right lambdoid suture. Notice that even this very small amount of synostosis causes significant deformation of the skull base as seen with downward displacement of the right mastoid bone (B) in relation to the normal mastoid bone (A).
Figure 12. 3-D CT scan of patient with premature closure of most of the left lambdoid suture.
Figure 13. CT scan showing thin slices of the skull and a closed left lambdoid suture.
Figure 14. Arrow on the left shows the closed suture whereas the arrow on the right shows an open suture on the other side.
FIGURE 15. 3-D CT scan shows the downward displacement of the mastoid bone in this child with left lambdoid synostosis.
Endoscopic Surgery
The goal of the surgery is to simply release and open the closed suture to allow the brain to resume its normal growth pattern and revert to a normal shape. Since the brain of an infant grows very rapidly, doubling in size during the first year of life, performing the procedure at an early age is of utmost importance. By using minimally invasive, endoscopic assisted techniques, such procedure can be done safely in very young babies. Once released, normalization of the head is aided with the use of custom made helmets (cranial orthosis) during the following year.
Positioning in Surgery
The patient is placed on his/her side on the operating room table (decubitus position) with the head being placed on a especially designed head holder. The head is turned so that the mastoid suture and the affected ear are easily reached for suture resection.
Skin Incisions
Two small incisions are made in order to access the closed suture. One is made near the midline and the other one behind the ear bridging both ends of the prematurely closed lambdoid suture.
RESULTS
Number of Patients: 25
Time Range: March 1998 to September 2018
Average Blood Loss: 16 ml's
Average Blood Transfusion Rate: 0%
Average Length of Hospitalization: 1.0 days
Average Surgical Time: 61 minutes
Number of Re-operations: None
Number of cases converted to CVR: None