Neurosurg. Rev. Achondroplasia: unusual bone abnormalities of the cervical spine 15 (1992) 143--145

Luigi Ferrante, Miehele Acqui, P. Celli, Antonio Santoro, and Aldo Fortuna

Department of Neurological Sciences, Neurosurgical Section, University of Rome "La Sapienza', Italy

Abstract

We report the case of an achondroplastic child in whom severe morphological and postural abnormalities of the cervical vertebrae were coupled with only mild and stable neurological deficits. The pathogenesis of the abnor- malities is discussed.

Keywords: Achondroplasia, cervical stenosis, X-rays, M.R.I.

I Introduction

Achondroplasia is an osteochondrodysplasia char- acterized by short stature with disproportionately short limbs and trident hand, macrocephaly with pronounced frontal eminences, depressed nasal bridge, and short trunk [1, 2].

The :neurological sequelae of malformations of the bone are mainly myeloradiculopathy secondary to vertebral canal abnormalities [3, 8], hypoacusis, hydrocephalus and brainstem impairment second- ary to alterations of the skull base [4, 10, 11], and peripheral nerve trunk impairment secondary to abnormalities of the skeletal segments of the limbs [2]. The most frequent clinical signs of spinal canal stenosis (s. c. s.) are those secondary to thoraco- lumbar stenosis in adults and those secondary to cervical and craniovertebral junction stenosis in children [5, 6].

We report the case of an achondroplastic child in whom unusual and severe morphological and pos- tural abnormalities of the cervical vertebrae were coupled with only mild and stable neurological deficits.

2 Case report

This 13-year-old boy, born at term by normal delivery to unrelated parents, presented nonfami- liar achondroplastic dwarfism. At birth his length was 49 cm and weight 2.8 kg. Macrocephaly, de- pressed nasal bridge, and prominent frontal em- inences were evident. Growth was retarded and consistently below the third percentile. Psychom- otor development, tested by Wechsler's intelligence scale for children, was within normal limits. Right from the first months of life, the child showed rhizomyelia. Head and neck posture was noticea- bly faulty, the short neck being sunk in the shoul- ders and the head slightly retroflexed. This dis- turbance was slowly but unremittingly progressive. From the age of 10 years the child showed mild weakness of the lower limbs and, from about a year later, of the upper limbs also. These symp- toms interfered only slightly with his normal ac- tivities and were stable. Occasional episodes of urinary urgency without incontinency were also reported.

The clinical findings were: height 120 cm, rhizo- myelia mainly of the lower limbs, macrocephaly, sunken glabella and prominent frontal eminences, short neck sunk in the shoulders and head retro- flexed. The boy also presented mild spastic tetra- paresis which did not, however, stop him from leading a regular life or being able to walk and use his upper limbs more or less normally; in fact this deficit was only evocable by tests of strength resistance. Lastly, there was hypesthesia to touch, heat, and pain below C3 level.

SSEE recorded after stimulation of the peroneal nerve, showed increased latency between the C7

�9 1992 by Walter de Grwter & Co. Berlin - New York

144 Ferrante et al., Achondroplasia of the cervical spine

and cortical recordings. Plain X-ray of the cervical spine (Figure 1) revealed severe vertebral dysplasia with pronounced abnormalities of morphology and alignment. MRI (Figure 2) confirmed the vertebral dysplasia and diffuse stenosis of the cerv- ical spine and also disclosed marked deviation and stretching of the spinal cord.

Given the mild and stable clinical pattern and the grave risks to the stability of the cervical spine that surgery would present, surgery was not of- fered. At follow-up about a year later there was no change in clinical and neuroradiological status.

3 Discuss ion

Since vertebrae develop through an endochondral ossification process, vertebral bone abnormalities are frequent in achondroplastic patients [6, 8]. In the case of the cervical spine these abnormalities are found chiefly in the first metameres and at the craniovertebral junction [4, 9]. Diffuse cervical stenosis is rarer [2, 7].

Our case presented unusual morphological defects throughout the cervical spine not found in other cases of achondroplasia with cervical stenosis.

Figure 1 a -t- b. Plain X-ray of the cervical spine showing severe vertebral dysplasia with pronounced abnormali- ties of morphology and alignment.

Figure 2 a + b. MRI of cervico-thoracic column (TR 2000, TE 100) showing diffuse stenosis of the cervical spine with marked deviation and stretching of the spinal cord.

Neurosurg. Rev. 15 (1992)

Ferrante et al., Achondroplasia of the cervical spine 145

It is hard to pinpoint the phases of alteration of vertebral development responsible for these bone malformations, although in achondroplasia the crucial phase is undoubtedly that of chondrifica- tion of the mesodermal rudiments which form bone by endochondral ossification.

Another peculiar feature of our case is the great discrepancy between the severe bone and postural abnormalities of the spine and the mild and stable clinical sequelae. Although it cannot be excluded that this situation is secondary to cranio-cervical t rauma suffered at delivery, this hypothesis seems unlikely because such a mechanism would have caused acute compression of the cervical cord whose formation was already at an advanced stage.

It appears more probable that the discrepancy between the clinical and neurological situation is due to a gradual adaptation of the cord to the anomalous development of the structures of the skeleton.

Treatment of cervical and craniospinal junction in achondroplasia is surgical and its purpose is to alleviate myeloradicular compression and prevent eventual acute bulbomedullary compression [2, 5, 6]. In our case the decision not to intervene sur- gically was motivated by the high risk of postop- erative instability of the cervical spine. In fact, the severe dysmorphism of the vertebral bodies and pedicles practically excluded any attempt at an- terior or posterior fixation.

References

[1] ASCENZI A, G MOTTURA: Trattato di anatomia pa- tologica per il medico pratico. Torino: UTET vol. II (1986) 1438--1439

[2] BAILEY JA: Orthopaedic aspects of achondroplasia. J Bone Joint Surg (am) 52a (1970) 1285-1301

[3] BLONDEAU M, D BRUNET, JM BLANCHE, C DE- BAUCHEZ, M ETIENNE: Compression de la moelle cervicale dans l'achondroplasie. Ann Pediatr 30 (1983) 651-656

[4] COHEN ME, AD ROSENTHAL, DD MATSON: Neu- rologic abnormalities in achondroplastic children. J Pediatr 71 (1967) 367-376

[5] HECHT JT, IJ BUTLER, C[ SCOTT JR: Long-term neurological sequelae in achondroplasia. Eur J Pe- diatr 143 (1984) 58-60

[6] MORGAN DF, RF YOUNG: Spinal neurological com- plications of achondroplasia. J Neurosurg 52 (1980) 463-472

[7] NELSON FW, WD GOLDIE, JT HECHT, IJ BUTLER, CI SCOTT: Short-latency somatosensory evoked po- tentials in the management of patients with achon- droplasia. Neurology (Cleveland) 34 (1984) 1053- 1058

[8] NELSON MA: Spinal stenosis in achondroplasia. Proc Roy Soc Med 65 (1983) 102

[9] STOKES CD, JA PHILLIPS, CO LEONARD, JP DORST, SE KOP~TS, JE TROJAK, DL BROWN: Respiratory complication of achondroplasia. J Pediatr 102 (1983) 534-- 541

[10] YAMADA H, S NAKAMURA, M TAJIMA, N KAGEYAMA: Neurological manifestations of pediatric achondro- plasia. J Neurosurg 54 (1981) 49-57

[11] YARINGTON CT, P SPRINGKLE: Hearing problems in certain forms of osteodystrophy: the chondrodys- trophies. Ear Nose Throat 46 (1967) 1136-1138

Submitted May 17, 1990. Accepted October 1, 1990.

Michele Acqui, M.D. Dipartimento di Scienze chirurgia Viale deU'Universit~i, 30a 1-00185 Rome Italy

Neurologiche Neuro-

Neurosurg. Rev. 15 (1992)