Archives ofDisease in Childhood 1990; 65: 851-855

Neurological manifestations of osteoid osteoma

L Kiers, L K Shield, W G Cole

AbstractThe clinical and radiological features of 38children with osteoid osteomas were analysedretrospectively. Twenty nine patients hadlesions of the femur (n=17) or tibia (n=12).The mean duration from the onset of symp-toms to diagnosis was 13-8 months. In sevenpatients the history of pain and abnormalitieson examination suggested a possible neuro-logical disorder. Fourteen of29 patients (48%)with femoral or tibial osteomas had localisedmuscle atrophy, and 10 patients (34%) haddiminished or absent deep tendon reflexes inthe affected limb. Two patients had painlesslesions. Six patients had normal plain radio-graphs. Delay in the diagnosis of osteoidosteoma may be prevented by the knowledgethat pain may be referred or radicular, that theconcomitant occurrence of muscle atrophyand depressed deep tendon reflexes arerelatively common findings, and that thecharacteristic radiological features may onlyappear late in the course of the disease.

Osteoid osteoma is a benign tumour of bone.Orthopaedic surgeons are well acquainted withthe lesion, which characteristically producesintense pain (initially nocturnal) and relieved bysalicylates.' Symptoms are often present formany months before the correct diagnosis ismade, partly because the characteristic radio-logical findings may not appear until late in thecourse of the disease.2 In addition, the tumourmay mimic certain neurological diseases,particularly spinal lesions, thereby resulting inunnecessary neuroradiological investigations.3Because of the varied presentation of osteoidosteoma and the inherent difficulty in makingthe diagnosis, we have analysed systematically

Royal Children'sHospital,Flemington Road,Parkville, Victoria,Australia 3052Department ofNeurologyL KiersL K ShieldDepartment ofOrthopaedic SurgeryW G ColeCorrespondence to:Dr Shield.Accepted 23 April 1990

the clinical and radiological features of thislesion, with particular reference to the signs andsymptoms suggestive of neurological disorder.

Patients, methods, and resultsThe records of the Royal Children's Hospitalfrom 1975-89 were searched for patients with adiagnosis of osteoid osteoma. Thirty eight wereidentified, in 36 of whom there was histologicalconfirmation of the diagnosis. The latter twopatients (cases 14 and 35) had typical clinicalhistories ofdeep nocturnal pain that was relievedby salicylates, and characteristic changes onplain radiographs and computed tomograms.All patients presenting with neurologicalsymptoms had been examined by a paediatricneurologist. There were 24 boys and 14 girls(ratio 1-7:1) with a mean age of 9 3 years (range3-17 years). Twenty nine patients (76%) hadlesions of the femur (n= 17) or tibia (n= 12). Ofthe remaining patients, lesions were located inthe proximal humerus (n=3), phalanges (n=2),vertebrae (n=2), ulna (n= 1), and calcaneus(n= 1). The mean duration from the onset ofsymptoms to diagnosis was 13-8 months (range2-60 months).

CLINICAL FEATURESOn the basis of the clinical features, mode ofpresentation, and site of the lesion, the patientswere divided into four groups.

Group ISeven patients were initially considered to haveneurological problems. The presenting symp-toms were predominantly disturbance of gaitand muscle wasting, with pain being a less

Table I Clinical features of patients in group I

Case Age Sex Site of Duration of Presenting features Findings on examinationNo (years) lesion symptoms

(months)

1 4 M Femur 2 Leg wasting; limp Wasted right quadriceps and gastrocnemius;4/5 weakness knee extension;absent right knee jerk

2 6 M Femur 12 Leg wasting; limp; Wasted left quadriceps; 4/5 weakness hipthigh pain flexion and knee extension; absent left

knee jerk3 17 F Femur 18 Leg wasting; anterior Wasted left quadriceps; absent left knee jerk

thigh pain4 8 F Femur 30 Leg wasting; limp; Wasted left quadriceps, gastrocnemius, and

anterior thigh pain glutei; depressed left knee and ankle jerk5 10 M Femur 6 Limp; anterior thigh pain; Wasted left quadriceps; depressed left

testicular pain knee jerk6 8 F Femur 2 Limp; thigh calf, and Wasted right quadriceps and gastrocnemius;

shin pain; leg wasting depressed right knee and ankle jerk7 6 M Tibia 12 Limp; anterior leg pain; Wasting and 4/5 weakness right tibialis

leg wasting anterior, hamstrings, gastrocnemius, andgluteii absent right ankle jerk

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prominent feature. Six patients had femoralosteomas and one had a tibial osteoma (table 1).Four patients had normal radiographs of thelumbosacral spine and normal myelogramsbefore the correct diagnosis was made. Allpatients had been initially referred to a neuro-logist.

Group 2Seven patients presented with orthopaedicproblems, with hip or leg pain, but on examin-ation were found to have localised musclewasting or depressed deep tendon reflexes, orboth, in the affected limb (table 2).

Group 3Fifteen patients, six with femoral osteomas and

nine with tibial osteomas, presented withoutneurological symptoms or signs. All except onepatient presented with either local or referredpain (table 3).

Group 4Nine patients had osteoid osteomas in sitesother than the femur or tibia. One patient withan osteoma in the proximal humerus presentedwith a palpable bony swelling resulting inbrachial plexus compression. The remainingpatients presented with localised pain (table 4).

Although there was considerable variation intheir clinical features, all patients except twoexperienced varying degrees of pain. Case 1presented with a limp and leg wasting withoutpain or tenderness, and case 21 presented with a

Table 2 Clinical features of patients in group 2

Case Age Sex Site of Duration of Presenting features Findings on examinationNo (years) lesion symptoms

(months)

8 6 F Femur 12 Thigh and shin pain Wasted left quadriceps, gastrocnemius;4/5 weakness knee extension; depressedleft knee and ankle jerk

9 4 M Femur 12 Thigh and leg pain Wasted left quadriceps; limp10 8 M Femur 60 Thigh pain Wasted left quadriceps; 1 cm discrepancy in

leg length11 12 M Femur 24 Knee pain Wasted left quadriceps and gastrocnemius;

depressed left knee jerk12 10 F Femur 12 Knee pain Wasted left quadriceps; depressed left

knee jerk, reduced hip flexion andabduction

13 14 M Tibia 3 Leg pain Wasted right gastrocnemius, 4/5 weaknessm plantar flexion

14 9 M Tibia 30 Leg pain, and bony Wasted left quadriceps; bony swellingswelling left tibia

Table 3 Clinical features of patients in group 3

Case Age Sex Site of Duration of Presenting features Findings on examinationNo (years) lesion symptoms

(months)

15 13 M Femur 4 Hip pain Not recorded16 9 M Femur 18 Knee and groin pain Not recorded17 12 F Femur 60 Thigh pain Not recorded18 10 M Femur 2 Hip and knee pain Reduced flexion and abduction left hip19 10 M Femur 6 Hip pain Reduced range of movement right hip20 3 M Femur 6 Thigh pain; limp Local tenderness21 13 M Tibia 18 Painless swelling, left tibia Bony swelling medial aspect left tibia22 14 M Tibia Not known Swelling left tibia, leg pain Bony swelling proximal left tibia23 9 M Tibia Not known Leg pain Not recorded24 8 M Tibia 2 Leg pain, swelling left tibia Bony swelling left tibia25 6 M Tibia 18 Ankle pain Bony swelling distal right tibia26 11 M Tibia 3 Leg pain; limp Not recorded27 11 F Tibia 12 Knee pain Bony swelling proximal right tibia28 9 F Tibia 2 Leg and ankle pain; limp Not recorded29 4 M Tibia 6 Leg pain; limp Bony swelling right tibia

Table 4 Clinical features of patients in group 4

Case Age Sex Site of Duration of Presenting features Findings on examinationNo (years) lesion symptoms

(months)

30 10 F Humerus 18 Elbow pain Tender swelling distal right humerus;reduced elbow extension

31 13 F Humerus 12 Arm pain Tender swelling upper medial humerus;wasting and weakness C5, 6, 7and sensory loss C5 and 6

32 14 F Humerus Not known Arm pain Not recorded33 6 F Proximal phalanx Not known Painful swelling Tender swelling right fifth finger

right fifth finger fifth finger34 9 M Distal phalanx Not known Pain second toe Not recorded

second toe35 11 M L5 vertebra 5 Low back pain Not recorded

(nocturnal)36 13 M S2 vertebra 12 Limp; left thigh and Wasting left hamstrings and calf;

buttock pain weakness left hamstrings, andquadriceps, positive Trendelenburg'stest

37 7 M Ulna Not known Pain left forearm Tender swelling left ulna38 16 F Calcaneus 12 Pain left foot Tender swelling lateral aspect left foot

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Neurological manifestations ofosteoid osteoma

painless swelling of the proximal tibia. Pain wasusually felt in the immediate region of the bonelesion, but many patients had referred pain,usually from a femoral osteoma to the knee.Some patients experienced pain in regionsremote from the lesion, without local pain. Case5 presented with left testicular pain, and laterpain in the left anterior thigh, from a lesion inthe left femoral neck. Case 6 had posteriorthigh, calf, and shin pain from an osteoma inthe femoral neck. Cases 11 and 12 experiencedonly knee pain, and case 16 had knee and groinpain from femoral osteomas. Case 36 complainedof radicular pain in the buttock and posteriorthigh from an osteoma in the left neural arch ofS2.Atrophy of some muscles of the affected limb

was noted in 14 (48%) of 29 patients withfemoral or tibial osteomas. One patient (case 36)with an osteoma in the left neural arch of S2 hadwasting of the left hamstring and calf muscles.Those muscles in the immediate region of thelesion were most commonly affected. In fivepatients with femoral osteomas, however, calfwasting was present in addition to wasting ofthe thigh (fig 1). One patient with a tibialosteoma had quadriceps as well as calf wasting

Figure I Case 1: wasting ofright vastus lateralis, vastusmedialis, and gastrocnemius in a patient with an osteoidosteoma ofthe rightfemoral neck.

(case 14), and one patient had wasting of thebuttock and hamstrings (case 7). Muscle weak-ness was uncommon despite the presence ofmuscle wasting. Two patients in group 1(neurological presentation) had mild quadricepsweakness, and one patient (case 7) with a tibialosteoma had mild weakness of tibialis anteriorand gastrocnemius. One patient in group 2 (case8) had mild weakness of quadriceps. Activity ofthe deep tendon reflexes of the affected limbwas diminished or absent in 10 (34%) of 29patients with femoral or tibial osteomas. Allseven patients in group 1, who were initiallythought to have neurological problems, haddepressed or absent reflexes in the affectedlimb.Twelve patients limped on the affected lower

limb, the diagnoses being femoral osteoma(n= 5), tibial osteoma (n=6), and sacral osteoma(n= 1). The limp was usually attributed to pain,although in three patients mild muscle weak-ness was also present. Local swelling, usuallyassociated with tenderness, was present in eight(67%) of 12 patients with tibial osteomas, twowith humeral osteomas, and in single patientswith lesions in the ulna, calcaneous, and proxi-mal phalanx of the fifth finger. No patient hadsensory loss on examination with the exceptionof case 31, in whom it was caused by compres-sion of the brachial plexus by the bony swelling.

IMAGING STUDIESAll patients had plain radiographs ofthe relevantregion, of which 30 (79%) showed findingsstrongly suggestive of osteoid osteoma. Onepatient (case 19) had findings that wereabnormal but equivocal (not being diagnosticof osteoid osteoma), and in one patient with anosteoma of the femoral neck (case 3), radio-graphs showed only subluxation of the hip joint.Six patients had normal plain radiographs of therelevant region of which one had an abnormaltomogram. Five of the six patients had femoralneck osteomas, and one had a vertebral osteoma.In one patient, abnormalities were noted ona repeat plain radiograph six months afterpresentation.

In 17 patients radionucleotide scans werecarried out. Ten were positive, showing intense,well defined, focal areas of increased activity onthe radioangiogram and blood pool studies.Seven were abnormal but not diagnostic ofosteoid osteoma. Fifteen patients had computedtomograms, all of which were abnormal withfindings strongly suggestive of osteoid osteoma.One patient did not undergo surgical excision ofthe lesion, as the parents withheld consent tooperation. The initial plain radiographs andcomputed tomogram showed the characteristicappearances of an intracortical osteoid osteoma.Repeat imaging studies 15 months later showedobvious healing of the lesion with only a smallarea of sclerosis on the plain radiograph, andnormal bone scan, correlating with clinicalresolution of pain.

HISTOLOGYThirty six patients underwent excision biopsy of

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their lesions, and histological confirmation ofthe diagnosis of osteoid osteoma was obtained.Microscopically all biopsies presented a charac-teristic picture with a well circumscribed nidusof osteoid and woven bone surrounded byregular plump fibroblasts, osteoblasts, andoccasional osteoclastic giant cells. Between thetrabeculae, there was a background stroma ofvascular fibrous tissue. Two patients whopresented as neurological problems (cases 1 and2) had muscle biopsies carried out to investigatetheir muscle wasting. In case 1 a needle biopsyspecimen from vastus lateralis showed predomi-nance of type 1 fibres with hypertrophy of type2A and 2B fibres, consistent with a 'fibre typedisproportion'. Case 2 had an open musclebiopsy specimen taken from adductor longus,which showed only mild atrophy of type 1 and2A fibres. Although probably within normallimits for this muscle, a neuropathic processcould not be entirely excluded.

DiscussionAn osteoid osteoma is a benign neoplasm ofbone with distinctive clinical signs andsymptoms. It is between two and three times ascommon in boys as in girls, with a maximumage incidence in the second and third decades oflife.' 2 The bones most commonly affected arethe femur and tibia, the lesions usually beinglocated near the shaft. In the vertebrae, themost common site is the neural arch.2 Almostwithout exception the initial symptom is pain,which is vague and intermittent at first butgradually increasing in severity. The pain isdescribed as boring or aching in character, andis characteristically worse at night and relievedby salicylates.'

Despite these classical features, the clinicaldiagnosis of osteoid osteoma can be notoriouslydifficult. The interval between the onset ofsymptoms and a correct diagnosis being made isseldom less than six months and it may be manyyears.' In our series the mean duration from theonset of symptoms to diagnosis was 13-8months. Delayed diagnosis may be explained bythe presence of atypical clinical features, par-ticularly neurological, and from lack of aware-

Figure 2 Case 12: computed tomogram showing cortical thickening of the leftfemoralneck medially, a lucent area within the cortex, and a calcified nidus (arrow).

ness that plain radiographs in the early stagescan be normal. Although the characteristic painis usually felt in the immediate region of thebone lesion, both 'referred' and 'radicular-like'pain are well described.-" Referred pain arisescommonly from three sites: (i) the lumbar spine,especially when the pars interarticularis isaffected-pain is referred to the abdomen orinto the leg; (ii) the region of the lesser trochan-ter of the femur-pain is commonly referred tothe knee8; and (iii) the posterior aspect of theupper third of the tibia-pain is referred up thethigt to the hip.9 In our series, three patientswith femoral osteomas experienced only referredpain in the knee without local pain, therebymisdirecting radiological studies. One patient(case 36) with an osteoma in the left neural archof S2 complained of buttock and thigh pain.Rare cases of painless, histologically diagnosed,osteoid osteomas have also been reported.'1-2The fact that osteoid osteomas may mimic

certain neurological diseases, in particular spinallesions, may also be a cause of delayed diagnosisresulting in unnecessary neuroradiologicalstudies. Localised atrophy of some muscles ofthe affected limb, decreased deep tendonreflexes, weakness, and rarely dermatomalsensory loss, are all well described. 1 " Rushtonet al also found abnormal straight leg raising intwo patients with lesions of the femoral shaft.3Halperin et al reported two children withosteoid osteomas of the proximal femur simulat-ing spinal root compression,4 and Youngincluded four patients with femoral osteomas inhis review of non-neurological lesions simulat-ing protruded intervertebral disc.S

Radiologically an osteoid osteoma can usuallybe seen as a well defined area of dense sclerosiswith a diameter of 05-1 cm in the centre ofwhich is a lucent nidus, which may containspeckled areas of calcification.' 13 Symptomscan precede the development of any radiologicalevidence of the tumour. Cortical osteoidosteomas usually result in cortical thickeningand a zone of sclerosis, but subperiosteal lesionsand those in cancellous bone produce much lesssclerosis and this may not be evident radio-logically.2 '3 Six of our patients had normalplain radiographs of the relevant regions, five ofwhom had femoral neck osteomas. Lesions inthis region, by virtue of the intracapsularlocation and cancellous nature of the bone,produce little sclerosis.2 This, in addition to thenormal irregularities in density and margins ofthe proximal end of the femur, can result indiagnostic difficulty. Radionucleotide scanningis indicated if the possibility of the diagnosis isborne in mind and if the plain radiographs arenormal. If plain films are abnormal but notdiagnostic, a computed tomogram with fineslices through the relevant region is recom-mended (fig 2).The histological appearance of an osteoid

osteoma varies with the age of the lesion andwith its site.7 The characteristic pain is pre-sumed to be related to the extremely vascularnature of the lesion, and increased tension andoedema within the lesion are thought to causethe pain by direct stimulation of local nervesaround the intraosseous vessels. Sherman and

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Neurological manifestations ofosteoid osteoma 855

McFarland showed that therewere unmyelinatednerve fibres in the fibrous zone around thenidus, and implicated them as the mediators ofthe pain.'4 Schulman and Dorfman, using aspecific silver stain, showed that there werenerve fibres within the nidus itself.'5 Thesefibres accompanied blood vessels and werepresumed to be derived from the autonomicnervous system.'4 The spinal origin of suchfibres implies they can conduct pain in aradicular distribution, which accounts for thereported 'radicular syndromes' associated withthese lesions,4 and the occasional local vaso-;motor phenomena characterised by increasedtemperature and hyperhydrosis.8 Makley andDunn found increased prostaglandin synthesis,particularly of prostaglandin E2, in three osteoidosteomas when compared with normal bone,and postulated that this may cause intense localpain by vasodilatation and hyperalgesia.'6

Treatment of osteoid osteoma consists of enbloc excision of the tumour and some surround-ing bone. Complete removal of the nidus isinvariably accompanied by almost immediaterelief of pain. 1 2 Two patients (cases 26 and 36)required reoperation for recurrent pain; in oneof them initial histopathological examinationfailed to confirm excision of the tumour nidus.One patient (case 6) who had a femoral neckosteoma, had the lesion successfully excised bya percutaneous technique under computedtomographic guidance. Prognosis from surgicalexcision was equally favourable in those patientspresenting with neurological symptoms andsigns as in those presenting with pain alone.The natural history of osteoid osteomas isdifficult to document because without biopsythe diagnosis cannot be proved, and biopsy maychange its normal development. Indirect evi-dence suggests, however, that the conditionruns a self limiting course.7 7 '8 In our series,case 14 did not undergo surgical excision of thelesion. Follow up imaging studies 15 monthsafter diagnosis showed obvious healing of thelesion, correlating with clinical resolution of thepain.

Diagnosis of osteoid osteoma requires anaccurate clinical history and an awareness of thepossibility of the diagnosis. The simultaneousmuscle atrophy and decreased deep tendonreflexes in the affected limb may erroneouslysuggest the presence of a primary neurologicaldisorder. Awareness of this, and of the occur-rence of radicular and referred pain, may avoidunnecessary neuroradiological investigations. Inthe context of a highly suggestive clinicalhistory, radionucleotide scanning should beundertaken even if plain radiographs are entirelynormal.

1 Black JA, Levick RK, Sharrard WJW. Osteoid osteoma andbenign osteoblastoma in childhood. Arch Dis Child 1979;54:459-65.

2 Swee RG, McLeod RA, Beabout JW. Osteoid osteoma.Detection, diagnosis and localization. Radiology 1979;130:117-23.

3 Rushton JG, Mulder DW, Lipscomb PR. Neurologicsymptoms with osteoid osteoma. Neurology 1955;5:794-7.

4 Halperin N, Gadoth N, Reif R, Axer A. Osteoid osteoma ofthe proximal femur simulating spinal root compression.Clin Orthop 1982;162:191-94.

5 Young HH. Non-neurological lesions simulating protrudedintervertebral disk. JAMA 1952;148:1101-5.

6 McCauley RGK, Goldberg MJ, Schwartz AM. Referred painin the lower leg-a cause of delayed diagnosis. SkeletalRadiol 1981;6:39-41.

7 Golding JSR. The natural history of osteoid osteoma, with areport of twenty cases. J BoneJoint Surg 1954;36B:218-29.

8 Chandler FA, Kaell HI. Osteoid osteoma. Arch Surg 1950;60:294-304.

9 Vaughan-Jackson OJ. Osteoid osteoma with unusual symp-toms. J Bone Joint Surg 1950;32B:368-9.

10 Lawrie TR, Aterman K, Sinclair AM. Painless osteoidosteoma. A report of two cases. Jf Bone Joint Surg1970;52A: 1357-63.

11 Sevitt S, Horn JS. A painless and calcified osteoid osteoma ofthe little finger. Journal of Pathology and Bacteriology1954;67:571-4.

12 Jaffe HL, Lichenstein L. Osteoid osteoma. Further experi-ence with this benign tumor of bone with special referenceto cases showing the lesion in relation to shaft cortices andcommonly misclassified as instances of sclerosing non-suppurative osteomyelitis or cortical-bone abscess. J BoneJotnt Surg [Am] 1940;22:645-82.

13 Flaherty RA, Pugh DG, Dockerty MB. Osteoid osteoma.AJR 1956;76:1041-51.

14 Sherman MS, McFarland G. Mechanism of pain in osteoidosteomas. South Med J 1965;58:163-6.

15 Schulman L, Dorfman HD. Nerve fibres in osteoid osteoma.J Bone Joint Surg 1970;52A:1351-6.

16 Makley JT, Dunn MJ. Prostaglandin synthesis by osteoidosteoma. Lancet 1982;ii:42.

17 Sherman MS. Osteoid osteoma: review of the literature andreport of thirty cases. J Bone Joint Surg [Am] 1947;29:918-30.

18 Simm RJ. The natural history of osteoid osteoma. Aust NZJSurg 1975;45:412-15.

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