Pediatric Radiology
Pediatr. Radiol. 8, 23-26 (1979)
9 by Springer-Verlag1979
Calcification of lntervertebral Discs in Childhood H. K : s o n Blomquist, M. Lindqvist, and S. Mattsson Departments of Pediatrics, Radiology and Orthopaedics, University of UmeS, Umefi, Sweden
Abstract. Fifteen cases of intervertebral disc calcifications have b e e n diagnosed in U m e ~ during a period of 14 years. In the literature up to n o w a b o u t 100 cases of intervertebral disc calcification have b e e n reported. O u r findings suggest that these calcifications are not as rare as has b e e n stated. T h e r e are b o t h s y m p t o m a t i c and silent cases. W h e n present the clinical s y m p t o m s comprise local pain in the neck, limitation of spinal m o v e m e n t s and sometimes fever and the condition m a y simulate meningitis. T h e radiological findings are p a t h o g n o m o n i c . T h e disc calcifications are most frequently f o u n d in boys especially in the cervical region. T h e etiology is u n k n o w n . T h e s y m p t o m s a p p e a r w h e n the calcification, for s o m e u n k n o w n reason, resorbs or herniates. Neurological s y m p t o m s are rare. T h e t r e a t m e n t is s y m p t o m a t i c and the clinical course self-limiting with c o m p l e t e rec o v e r y within a few weeks.
Key words: Calcification of intervertebral discs in children
disc, either h o m o g e n e o u s or fragmented. Sometimes it causes an indentation in the surrounding vertebral bodies (Fig. 1). T h e aim of the present study was to see if calcification of the discs in children really is as rare as has b e e n previously r e p o r t e d and also to present o t h e r features of this disease.
Material At the University Hospital of Ume~, Sweden 15 cases of intervertebral disc calcification in children aged 4-14 years have been diagnosed over a period of 14 years (Table 1). Pain and stiffness in the neck were the indications for radiological examination in the symptomatic cases. The asymptomatic cases were diagnosed incidently in children examined for other reasons 1.
Results D a t a a b o u t the intervertebral disc calcifications summ a r i z e d f r o m the literature and f r o m o w n cases are tabulated in tables 1-4. T h e level of the calcifications are shown in Figure 2.
Table 1. Age and sex distribution of children with intervertebral Intervertebral-disc calcification in childhood constitutes a clinical s y n d r o m e characterized by the following factors: pain, limitation of spinal m o v e m e n t , inflammation, disc calcification and a self-limited clinical course [6]. However,. a s y m p t o m a t i c cases have also b e e n described, especially in the thoracic and l u m b a r parts of the spine [21]. E v e r since the first case was r e p o r t e d by B a r o n in 1924 [1], n u m e r o u s case reports have b e e n p u b lished, with m o s t authors considering the condition to be very u n c o m m o n . R a d i o g r a p h i c a l l y there is a m o r e o r less dense calcification in the middle part of the intervertebral
disc calcifications
Total number Boys Girls Sex not reported Age, mean in years
Literature cases
Own cases
97 54 42 1 7
15 9 6 I0
1 Radiography of the spine was carried out in one boy because of toe-walking and in one girl because of retarded growth. In two other girls the condition was diagnosed on chest films taken because of recurrent episodes of fever.
0301-0449/79/0008/0023/$01.00
Fig. 1. a frontal and b lateral tomogram of the thoracic spine demonstrating a calcification in the nucleus pulposus of the Th5-6 disc. The vertebral body of the Th5 has an indentation of its lower margin (--~) caused by the calcified disc a
b
Table 2. Radiographic findings in intervertebral disc calcifications summarized from the literature and from our cases Literature: Inci- Own: Incidence dence number/ number/cases cases recorded recorded Total number of calcifications Single calcification Multiple calcifications Number of calcifications in one child Herniation of calcification in: Cervical level Thoracic level Lumbar level Radiographic disappearance within a year in symptomgiving cases
169/97 58/97 39/97
19/15 12/15 3/15
1-7/97
1-3 / 15
9/87 4/73 1/9
3/7 0/11 0/1
36/65
6/6
Table 3. Symptoms, signs and time for clinical recovery in intervertebral disc calcifications summarized from the literature and from our
cases
Literature: incidence number/cases recorded
Own: incidence number/cases recorded
Back pain Limitation of movements Scoliosis Neurological symptoms Asymptomatic
70/97 52/97 44/97 7/97 15/97
11/15 9/15 0/15 0/15 4/15
Fever > 38 degrees centigrade EMSR > 20 mm Leukocyte number > 10000 Weeks for clinical recovery, mean (range)
29/52 9/11 9/13 2.8 (2-12)/44
5/10 5/10 6/10 1 (1-2)/10
Table 4. Possible etiological factors in intervertebral disc calcification summarized from the literature and from own cases
Discussion
Until now about 100 cases of calcification of intervertebral discs in children have been reported in the literature. Some authors have published comprehensive references [2, 5, 9, 10, 11, 22, 24, 23, 18]. Previously, intervertebral disc calcification has been considered to be uncommon in children [22, 12, 23, 2, 11, 14]. However, a few investigators [24, 16] have stated that the disease is not rare but unob-
Congenital abnormalities Abnormal delivery Recent respiratory infection Recent trauma
Literature: incidence number/cases recorded
Own: incidenee number/cases recorded
8/15 3/18 28/40 18/33
0/15 4a/11 4/15 2/15
a Two breech presentations, one face presentation and one forceps delivery
served in clinical and radiological diagnosis. This is supported by the authors who during the last fourteen years have found no less than fifteen cases among a population of about 100,000 people in a district of northern Sweden. From an ecological point of view it is unlikely that the real incidence is higher in our district than elsewhere. In boys the predominant sites of the calcification are the cervical discs whereas in girls they are distributed more uniformly over the spine [11]. This is in accord with the present findings. Of the fifteen cases, four were symptomless and in only one of these the calcification was situated in the cervical region. In the literature thirteen assymptomatic cases have been described earlier. However, in only one case with multiple calcifications one of them was situated in the CT-Thl level [14]. Thus cervical disc calcification as an incidental finding seems to be rare. It is not known how long it takes for the calcification to develop prior to the onset of symptoms. In one case [15] no calcification was found in two cervical discs two months before onset of symptoms. The view of the authors is, however, that in most cases the calcified material has been laid down a long time before the symptoms appear. In cases with multiple calcifications only those
a
b
corresponding to the symptom-giving level diminish after the period of clinical disease. Perhaps multiple location of disc calcification is rather common but not diagnosed because only the symptom-giving part of Boys
Girls
~ C
[4
rhl ~
I
10 t2 L1 2 3 4
E'91 i
i
i
,, , i
15
10
5
10
i
0 1
5
Number
of
10 cases
Fig. 2. Level distribution of 188 intervertebral disc calcifications in 112 children (Our cases hatched)
c
Fig. 3 a-c. Twelve years old boy with asymptomatic intervertebral disc calcification, a Lateral view of the cervical spine 2 days after the onset of neck pain. Calcification (--+) of the intervertebral disc C6-7. b Lateral view 4 months later, after complete clinical recovery. Decreased size and density of the calcification (--+). c Lateral view 2 years later. The calcification has disappeared completely, and there is no residual deformity of the disc or vertebral bodies
26
the spine has been radiologically examined. Furthermore multiple calcifications are only seldom located in neighbouring discs. The radiographic findings are identical in cases with and without clinical symptoms. The symptomgiving calcifications tend to disappear within a year (Figs. 3 a-c), while the asymptomatic disc calcifications remain unchanged. Only a few other conditions are associated with disc calcification. Some cases of congenital malformation with block vertebrae show calcification in the rudimentary disc between the affected vertebral bodies. Vitamin D poisoning can give rise to calcification in the annulus fibrosus. Other conditions with disc calcification, such as degenerative changes and alcaptonuria, are not found in the pediatric age group. In fact the radiological findings in cases of idiopathic disc calcification in children are so typical that they can be regarded as pathognomonic for what they are. The clinical symptoms may easily be misinterpreted as those of bacterial discitis or spondylitis. The early radiological findings in the latter conditions are a narrowing of the disc space as well as destruction of the end-plates of the surrounding vertebral bodies. Calcification of the disc does not occur in cases of bacterial spondylitis. The etiology of the disease is unknown [24, 12]. The discs still have their own vessels at this age [3, 6] and the calcification can possibly develop within a few weeks [15]. Finally most of the calcified material is generally resorbed and/or herniated in some weeks or months from the start of the clinical symptoms [4, 2]. The etiological factors most often referred to are trauma and infection. Birth trauma has been mentioned as one possible causative factor [8, 19] and this seems to apply in at least four of our cases. Perhaps there are several reasons for initiation of an inflammatory process resulting in deposition of calcified material in the nucleus pulposus of a disc of a child's spine. The sex and level differences could support this assumption. The anterior or posterior herniation seems, in some cases, to be a part of the pathological process rather than a rare complication [12, 22, 7]. When symptoms appear they are acute but soon disappear spontaneously regardless of the treatment. All our patients with symptoms had dorsal pain with a certain degree of stiffness in the affected region of the dorsum. About half of them had some fever and a slight increase of the EMSR. Neurological symptoms are rare and did not appear in our patients. The case reports in the literature make it clear that operation is hardly ever indicated [12, 18, 13, 17].
H. K: son Blomquist et al.: Intervertebral Discs
References 1. Baron, A.: Clber eine neue Erkrankung der Wirbelsfiule. Jahrb. Kinderheilkd. 104, 357 (1924) 2. Brohm, O., Lang Petersen, J.: Calcificatio disci intervertebrales hos born. Nord. Med. 31, 921 (1971) (in Danish) 3. B6hmig, R.: Arch. Klin. Chir. 158, 374 (1930) 4. Caffey, J.: Pediatric x-ray diagnosis. 5th edition, p. 1135. Chicago: Year Book Publ. 1967 5. Cronquist, S., Mortensson, W.: Protrusion of calcified cervical discs into the spinal canal in children. Neuroradiology 9, 223 (1975) 6. DePalma, A., Rothman, R.: The intervertebral disc. Philadelphia, Toronto: Saunders 1970 7. Eyring, E. J., Peterson, C. A., Bjornson, D. R.: Intervertebraldisc calcification in childhood: a distinct clinical syndrome. J. Bone Joint Surg. 46A, 1432 (1964) 8. Koteles, G., Donko, J.: Bandscheibenverkalkungen der Halswirbels~iule im Kindesalter. Z. Kinderchir. 12, 487 (1973) 9. Klaus, E., Nekula, J.: Cervikale Bandscheibenverkalkung beim Kind. Radiologe 15, 59 (1975) 10. Lehner, M., Richter, G.: Idiopathic calcification of the intervertebral disc and prevertebral ligament. J. Pediatr. Surg. 6, 979 (1973) 11. Lindberg, T.: Intervertebral calcinosis in childhood. Ann. Paediatr. 201, 173 (1963) 12. Mainzer, F.: Herniation of the nucleus pulposus. A rare complication of intervertebral disc calcification in children. Radiology 10"7, 167 (1973) 13. Maccartee, C.C., Griffin, P. P., Byrd, E.B.: Ruptured calcified thoracic disc in a child. J. Bone Joint Surg. 54A, 1272 (1972) 14. Melnick, J. C., Silverman, F.N.: Intervertebral disc calcification in childhood. Radiology 80, 399 (1963) 15. Mikity, V. G., Isenbarger, J.: Intervertebral disc calcification in children. Am. J. Roentgenol. 95, 200 (1965) 16. Morris, J., Niebauer, J.: Calcification of the cervical intervertebral disc. Am. J. Dis. Child. 106, 295 (1963) 17. Newton, T.H.: Cervical intervertebral disc calcification in children. J. Bone Joint Surg. 40A, 107 (1958) 18. Pehrson, M., Sj6gren, I., Westphal, O., Wranne, L.: Akut torticollis hos barn. L/ikartidningen 48, 4787 (1968) (in Swedish) 19. Pierce, F., Hanafee, W.: Calcified cervical discs in a child. Calif. Med. 92, 283 (1960) 20. Schechter, L. S., Smith, A., Pearl, M.: Intervertebral disc calcification in childhood. Am. J. Dis. Child. 123, 608 (1972) 21. Schorr, S., Adler, E.: Calcified intervertebral disc in children and adults. Acta Radiol. 41, 498 (1954) 22. Stewart, P., Silbiger, M., Wolfson, S.: Intervertebral disc calcification in childhood. Clin. Pediatr. (Phila.) 4, 363 (1974) 23. Sutton, J., Turcotte, B.: Posterior herniation of calcified intervertebral discs in children. J. Can. Assoc. Radiol. 24, 131 (1973) 24. Swick, H.: Calcification of intervertebral discs in childhood. J. Pediatr. 2, 364 (1975) 25. Weens, H. S.: Calcification of the intervertebral discs in childhood. J. Pediatr. 26, 178 (1945) Date of final acceptance: November 15, 1978
Dr. Melker Lindqvist Department of Radiology University Hospital of Umegt S-90185 UmeS, Sweden
Pediatr. Radiol. 8, 23-26 (1979)
9 by Springer-Verlag1979
Calcification of lntervertebral Discs in Childhood H. K : s o n Blomquist, M. Lindqvist, and S. Mattsson Departments of Pediatrics, Radiology and Orthopaedics, University of UmeS, Umefi, Sweden
Abstract. Fifteen cases of intervertebral disc calcifications have b e e n diagnosed in U m e ~ during a period of 14 years. In the literature up to n o w a b o u t 100 cases of intervertebral disc calcification have b e e n reported. O u r findings suggest that these calcifications are not as rare as has b e e n stated. T h e r e are b o t h s y m p t o m a t i c and silent cases. W h e n present the clinical s y m p t o m s comprise local pain in the neck, limitation of spinal m o v e m e n t s and sometimes fever and the condition m a y simulate meningitis. T h e radiological findings are p a t h o g n o m o n i c . T h e disc calcifications are most frequently f o u n d in boys especially in the cervical region. T h e etiology is u n k n o w n . T h e s y m p t o m s a p p e a r w h e n the calcification, for s o m e u n k n o w n reason, resorbs or herniates. Neurological s y m p t o m s are rare. T h e t r e a t m e n t is s y m p t o m a t i c and the clinical course self-limiting with c o m p l e t e rec o v e r y within a few weeks.
Key words: Calcification of intervertebral discs in children
disc, either h o m o g e n e o u s or fragmented. Sometimes it causes an indentation in the surrounding vertebral bodies (Fig. 1). T h e aim of the present study was to see if calcification of the discs in children really is as rare as has b e e n previously r e p o r t e d and also to present o t h e r features of this disease.
Material At the University Hospital of Ume~, Sweden 15 cases of intervertebral disc calcification in children aged 4-14 years have been diagnosed over a period of 14 years (Table 1). Pain and stiffness in the neck were the indications for radiological examination in the symptomatic cases. The asymptomatic cases were diagnosed incidently in children examined for other reasons 1.
Results D a t a a b o u t the intervertebral disc calcifications summ a r i z e d f r o m the literature and f r o m o w n cases are tabulated in tables 1-4. T h e level of the calcifications are shown in Figure 2.
Table 1. Age and sex distribution of children with intervertebral Intervertebral-disc calcification in childhood constitutes a clinical s y n d r o m e characterized by the following factors: pain, limitation of spinal m o v e m e n t , inflammation, disc calcification and a self-limited clinical course [6]. However,. a s y m p t o m a t i c cases have also b e e n described, especially in the thoracic and l u m b a r parts of the spine [21]. E v e r since the first case was r e p o r t e d by B a r o n in 1924 [1], n u m e r o u s case reports have b e e n p u b lished, with m o s t authors considering the condition to be very u n c o m m o n . R a d i o g r a p h i c a l l y there is a m o r e o r less dense calcification in the middle part of the intervertebral
disc calcifications
Total number Boys Girls Sex not reported Age, mean in years
Literature cases
Own cases
97 54 42 1 7
15 9 6 I0
1 Radiography of the spine was carried out in one boy because of toe-walking and in one girl because of retarded growth. In two other girls the condition was diagnosed on chest films taken because of recurrent episodes of fever.
0301-0449/79/0008/0023/$01.00
Fig. 1. a frontal and b lateral tomogram of the thoracic spine demonstrating a calcification in the nucleus pulposus of the Th5-6 disc. The vertebral body of the Th5 has an indentation of its lower margin (--~) caused by the calcified disc a
b
Table 2. Radiographic findings in intervertebral disc calcifications summarized from the literature and from our cases Literature: Inci- Own: Incidence dence number/ number/cases cases recorded recorded Total number of calcifications Single calcification Multiple calcifications Number of calcifications in one child Herniation of calcification in: Cervical level Thoracic level Lumbar level Radiographic disappearance within a year in symptomgiving cases
169/97 58/97 39/97
19/15 12/15 3/15
1-7/97
1-3 / 15
9/87 4/73 1/9
3/7 0/11 0/1
36/65
6/6
Table 3. Symptoms, signs and time for clinical recovery in intervertebral disc calcifications summarized from the literature and from our
cases
Literature: incidence number/cases recorded
Own: incidence number/cases recorded
Back pain Limitation of movements Scoliosis Neurological symptoms Asymptomatic
70/97 52/97 44/97 7/97 15/97
11/15 9/15 0/15 0/15 4/15
Fever > 38 degrees centigrade EMSR > 20 mm Leukocyte number > 10000 Weeks for clinical recovery, mean (range)
29/52 9/11 9/13 2.8 (2-12)/44
5/10 5/10 6/10 1 (1-2)/10
Table 4. Possible etiological factors in intervertebral disc calcification summarized from the literature and from own cases
Discussion
Until now about 100 cases of calcification of intervertebral discs in children have been reported in the literature. Some authors have published comprehensive references [2, 5, 9, 10, 11, 22, 24, 23, 18]. Previously, intervertebral disc calcification has been considered to be uncommon in children [22, 12, 23, 2, 11, 14]. However, a few investigators [24, 16] have stated that the disease is not rare but unob-
Congenital abnormalities Abnormal delivery Recent respiratory infection Recent trauma
Literature: incidence number/cases recorded
Own: incidenee number/cases recorded
8/15 3/18 28/40 18/33
0/15 4a/11 4/15 2/15
a Two breech presentations, one face presentation and one forceps delivery
served in clinical and radiological diagnosis. This is supported by the authors who during the last fourteen years have found no less than fifteen cases among a population of about 100,000 people in a district of northern Sweden. From an ecological point of view it is unlikely that the real incidence is higher in our district than elsewhere. In boys the predominant sites of the calcification are the cervical discs whereas in girls they are distributed more uniformly over the spine [11]. This is in accord with the present findings. Of the fifteen cases, four were symptomless and in only one of these the calcification was situated in the cervical region. In the literature thirteen assymptomatic cases have been described earlier. However, in only one case with multiple calcifications one of them was situated in the CT-Thl level [14]. Thus cervical disc calcification as an incidental finding seems to be rare. It is not known how long it takes for the calcification to develop prior to the onset of symptoms. In one case [15] no calcification was found in two cervical discs two months before onset of symptoms. The view of the authors is, however, that in most cases the calcified material has been laid down a long time before the symptoms appear. In cases with multiple calcifications only those
a
b
corresponding to the symptom-giving level diminish after the period of clinical disease. Perhaps multiple location of disc calcification is rather common but not diagnosed because only the symptom-giving part of Boys
Girls
~ C
[4
rhl ~
I
10 t2 L1 2 3 4
E'91 i
i
i
,, , i
15
10
5
10
i
0 1
5
Number
of
10 cases
Fig. 2. Level distribution of 188 intervertebral disc calcifications in 112 children (Our cases hatched)
c
Fig. 3 a-c. Twelve years old boy with asymptomatic intervertebral disc calcification, a Lateral view of the cervical spine 2 days after the onset of neck pain. Calcification (--+) of the intervertebral disc C6-7. b Lateral view 4 months later, after complete clinical recovery. Decreased size and density of the calcification (--+). c Lateral view 2 years later. The calcification has disappeared completely, and there is no residual deformity of the disc or vertebral bodies
26
the spine has been radiologically examined. Furthermore multiple calcifications are only seldom located in neighbouring discs. The radiographic findings are identical in cases with and without clinical symptoms. The symptomgiving calcifications tend to disappear within a year (Figs. 3 a-c), while the asymptomatic disc calcifications remain unchanged. Only a few other conditions are associated with disc calcification. Some cases of congenital malformation with block vertebrae show calcification in the rudimentary disc between the affected vertebral bodies. Vitamin D poisoning can give rise to calcification in the annulus fibrosus. Other conditions with disc calcification, such as degenerative changes and alcaptonuria, are not found in the pediatric age group. In fact the radiological findings in cases of idiopathic disc calcification in children are so typical that they can be regarded as pathognomonic for what they are. The clinical symptoms may easily be misinterpreted as those of bacterial discitis or spondylitis. The early radiological findings in the latter conditions are a narrowing of the disc space as well as destruction of the end-plates of the surrounding vertebral bodies. Calcification of the disc does not occur in cases of bacterial spondylitis. The etiology of the disease is unknown [24, 12]. The discs still have their own vessels at this age [3, 6] and the calcification can possibly develop within a few weeks [15]. Finally most of the calcified material is generally resorbed and/or herniated in some weeks or months from the start of the clinical symptoms [4, 2]. The etiological factors most often referred to are trauma and infection. Birth trauma has been mentioned as one possible causative factor [8, 19] and this seems to apply in at least four of our cases. Perhaps there are several reasons for initiation of an inflammatory process resulting in deposition of calcified material in the nucleus pulposus of a disc of a child's spine. The sex and level differences could support this assumption. The anterior or posterior herniation seems, in some cases, to be a part of the pathological process rather than a rare complication [12, 22, 7]. When symptoms appear they are acute but soon disappear spontaneously regardless of the treatment. All our patients with symptoms had dorsal pain with a certain degree of stiffness in the affected region of the dorsum. About half of them had some fever and a slight increase of the EMSR. Neurological symptoms are rare and did not appear in our patients. The case reports in the literature make it clear that operation is hardly ever indicated [12, 18, 13, 17].
H. K: son Blomquist et al.: Intervertebral Discs
References 1. Baron, A.: Clber eine neue Erkrankung der Wirbelsfiule. Jahrb. Kinderheilkd. 104, 357 (1924) 2. Brohm, O., Lang Petersen, J.: Calcificatio disci intervertebrales hos born. Nord. Med. 31, 921 (1971) (in Danish) 3. B6hmig, R.: Arch. Klin. Chir. 158, 374 (1930) 4. Caffey, J.: Pediatric x-ray diagnosis. 5th edition, p. 1135. Chicago: Year Book Publ. 1967 5. Cronquist, S., Mortensson, W.: Protrusion of calcified cervical discs into the spinal canal in children. Neuroradiology 9, 223 (1975) 6. DePalma, A., Rothman, R.: The intervertebral disc. Philadelphia, Toronto: Saunders 1970 7. Eyring, E. J., Peterson, C. A., Bjornson, D. R.: Intervertebraldisc calcification in childhood: a distinct clinical syndrome. J. Bone Joint Surg. 46A, 1432 (1964) 8. Koteles, G., Donko, J.: Bandscheibenverkalkungen der Halswirbels~iule im Kindesalter. Z. Kinderchir. 12, 487 (1973) 9. Klaus, E., Nekula, J.: Cervikale Bandscheibenverkalkung beim Kind. Radiologe 15, 59 (1975) 10. Lehner, M., Richter, G.: Idiopathic calcification of the intervertebral disc and prevertebral ligament. J. Pediatr. Surg. 6, 979 (1973) 11. Lindberg, T.: Intervertebral calcinosis in childhood. Ann. Paediatr. 201, 173 (1963) 12. Mainzer, F.: Herniation of the nucleus pulposus. A rare complication of intervertebral disc calcification in children. Radiology 10"7, 167 (1973) 13. Maccartee, C.C., Griffin, P. P., Byrd, E.B.: Ruptured calcified thoracic disc in a child. J. Bone Joint Surg. 54A, 1272 (1972) 14. Melnick, J. C., Silverman, F.N.: Intervertebral disc calcification in childhood. Radiology 80, 399 (1963) 15. Mikity, V. G., Isenbarger, J.: Intervertebral disc calcification in children. Am. J. Roentgenol. 95, 200 (1965) 16. Morris, J., Niebauer, J.: Calcification of the cervical intervertebral disc. Am. J. Dis. Child. 106, 295 (1963) 17. Newton, T.H.: Cervical intervertebral disc calcification in children. J. Bone Joint Surg. 40A, 107 (1958) 18. Pehrson, M., Sj6gren, I., Westphal, O., Wranne, L.: Akut torticollis hos barn. L/ikartidningen 48, 4787 (1968) (in Swedish) 19. Pierce, F., Hanafee, W.: Calcified cervical discs in a child. Calif. Med. 92, 283 (1960) 20. Schechter, L. S., Smith, A., Pearl, M.: Intervertebral disc calcification in childhood. Am. J. Dis. Child. 123, 608 (1972) 21. Schorr, S., Adler, E.: Calcified intervertebral disc in children and adults. Acta Radiol. 41, 498 (1954) 22. Stewart, P., Silbiger, M., Wolfson, S.: Intervertebral disc calcification in childhood. Clin. Pediatr. (Phila.) 4, 363 (1974) 23. Sutton, J., Turcotte, B.: Posterior herniation of calcified intervertebral discs in children. J. Can. Assoc. Radiol. 24, 131 (1973) 24. Swick, H.: Calcification of intervertebral discs in childhood. J. Pediatr. 2, 364 (1975) 25. Weens, H. S.: Calcification of the intervertebral discs in childhood. J. Pediatr. 26, 178 (1945) Date of final acceptance: November 15, 1978
Dr. Melker Lindqvist Department of Radiology University Hospital of Umegt S-90185 UmeS, Sweden
