Rapid Forehead Ossification due to a Subperiosteal Hematoma in a Patient With Neurofibromatosis Type 1.

Rapid ossification due to a subperiosteal hematoma in extremities has occasionally been documented in patients with neurofibromatosis type 1, but it has not been reported in the maxillofacial region. The authors present the first case of a subperiosteal hematoma in the forehead. A 36-year-old man presented with a rapidly swelling firm, fixed, 8×10 cm forehead mass. It became evident shortly after a fine-needle aspiration biopsy. Computed tomography imaging 2 months after the biopsy showed a hematoma that was encapsulated by a surrounding layer of ossification. Magnetic resonance imaging displayed a fluid-fluid level under the ossified area. These characteristic images led us to diagnose this rare lesion as a subperiosteal hematoma with ossification. Rapid ossification is a characteristic imaging finding of subperiosteal hematoma, which makes definitive diagnosis easy. It becomes imperative to underscore the potential risks of fine-needle aspiration in proximity to the periosteum in patients with neurofibromatosis type 1.

Periosteal Pathologic Conditions: Imaging Findings and Pathophysiology.

The periosteum plays a key role in bone health and is a primary means by which the skeleton responds to a wide range of insults, both benign and malignant. Developmental and histologic features of normal periosteum explain some of the characteristic imaging findings seen in the setting of bone abnormalities. Patterns of periosteal reaction, both in morphology and distribution, are key to distinguishing benign or physiologic periosteal reaction from types of periosteal reaction that warrant further evaluation. The authors review the histologic features, distribution, and development of normal periosteum. Nonaggressive and aggressive types of periosteal reaction are presented with key associations for each. The presence of nonaggressive types of periosteal reaction implies that the underlying process affecting the bone is slow enough that the periosteum is able to heal it or contain it in an organized manner. In contrast, aggressive types of periosteal reaction are seen when the underlying bone insult outpaces the ability of the periosteum to contain it. Image-guided biopsies of lesions with periosteal reaction should be used to sample the site of the most aggressive pattern, as this approach can aid in accurate histologic grading and in detection of tumor cells and bone matrix. The distribution of periosteal abnormalities is as important as the morphology, with a diffuse periosteal reaction favoring systemic causes such as rheumatologic, metabolic, and hematologic conditions compared with a more localized periosteal reaction. Important causes of localized and diffuse periosteal reaction are discussed in a systems-based format, with an emphasis on clinically important causes. © RSNA, 2022.

Ultrasonography of the bone surface in children: normal and pathological findings in the bone cortex and periosteum.

Ultrasound (US) is widely used in pediatric musculoskeletal pathology at all ages. Although the focus is often on soft tissues, joints and cartilage, the examiner might be confronted with changes in the underlying bone surface that are important to understand and integrate in the diagnosis. This article illustrates the normal US aspects of the cortical bone surface and periosteum, as well as the most common US anomalies seen in infections, trauma and bone tumors in children.

Periosteum coverage versus collagen-membrane coverage in periodontally accelerated osteogenic orthodontics: a randomized controlled clinical trial in Class II and Class III malocclusions.

BACKGROUND: Periodontal accelerated osteogenic orthodontics (PAOO) is a widely-used clinical procedure that combines selective alveolar corticotomy, particulate bone grafting, and the application of orthodontic forces. Different modifications of PAOO such as collagen-membrane coverage can better benefit patients from preventing displacement of grafts. Due to its stability, collagen-membrane coverage gradually gained popularity and became a widely-used procedure in traditional PAOO technique. OBJECTIVES: To quantitatively investigate the radiographic changes of alveolar bone, periodontal soft tissue changes of the mandibular anterior teeth and postoperative complications in periosteum-covered techniques compared with traditional surgical technique in PAOO. METHODS: Orthodontic camouflage for dental Class II or decompensation for skeletal Class III malocclusions were included; Patients with bone defects on the buccal aspects of the anterior mandible regions confirmed by clinical and radiographic examination were randomly divided into the periosteum coverage group or traditional technique group for PAOO. Cone-beam computerized tomography (CBCT) scans were obtained before treatment (T0) and 1 week (T1) and 12 months (T2) after operation. The primary outcome variable was the vertical alveolar bone level (VBL), the secondary evaluation parameters included labial horizontal bone thickness at the midpoint of the middle third (MHBT) or apical third (AHBT) to the limit of the labial cortical surface during a 12-month follow-up. Postoperative sequelae were evaluated after 2 days and 7 days in both the groups. Periodontal parameters were analyzed at T0 and T2. RESULTS: Thirty-six adult subjects were eligible and recruited in the present study. Although experimental group exhibited more severe infection, no significant differences of the postoperative symptoms or periodontal parameters was found between the 2 groups (P > 0.05). All patients were examined respectively using CBCT at baseline (T0), postoperative 1 week (T1) and 12 months (T2). Both alveolar bone height and width increased from T0 to T1 (P < 0.001) and then reduced from T1 to T2 (P < 0.001) in both groups. However, significant bone augmentation was achieved in each group from T0 to T2 (P < 0.001). Furthermore, the vertical alveolar bone augmentation in the experimental group increased significantly than that in the traditional surgery (P < 0.05). CONCLUSIONS: Compared with traditional PAOO surgery, the periosteum-covered technique provides superior graft stabilization and satisfactory vertical bone augmentation in the labial mandibular anterior area.

Changes in the intra- and peri-cellular sclerostin distribution in lacuno-canalicular system induced by mechanical unloading.

INTRODUCTION: Mechanical stimuli regulate Sclerostin (Scl), a negative regulator of bone formation, expression in osteocytes. However, the detailed Scl distribution in osteocytes in response to mechanical unloading remains unclear. MATERIALS AND METHODS: Twelve-week-old male rats were used. The sciatic and femoral nerves on the right side were excised as mechanical unloading treatment. A sham operation was performed on the left side. One week after neurotrauma, the bone density of the femora was evaluated by peripheral quantitative computed tomography, and immunofluorescence was performed in coronal sections of the femoral diaphysis. The mean fluorescence intensity and fluorescent profile of Scl from the marrow to the periosteal side were analyzed to estimate the Scl expression and determine to which side (marrow or periosteal) the Scl prefers to distribute in response to mechanical unloading. The most sensitive region indicated by the immunofluorescence results was further investigated by transmission electron microscopy (TEM) with immunogold staining to show the Scl expression changes in different subcellular structures. RESULTS: In femur distal metaphysis, neurotrauma-induced mechanical unloading significantly decreased the bone density, made the distribution of Scl closer to the marrow on the anterior and medial side, and increased the Scl expression only on the lateral side. TEM findings showed that only the expression of Scl in canaliculi was increased by mechanical unloading. CONCLUSIONS: Our results showed that even short-term mechanical unloading is enough to decrease bone density, and mechanical unloading not only regulated the Scl expression but also changed the Scl distribution in both the osteocyte network and subcellular structures.

Spontaneous subperiosteal orbital hematoma in a patient with chronic sinusitis.

Periorbital swelling is a common presentation to the emergency department (ED), and its etiology can range from benign to acutely vision-threatening. Orbital subperiosteal hematoma is a rare ED diagnosis that is typically associated with trauma, though can infrequently occur spontaneously in the setting of sudden elevations in cranial venous pressure, bleeding diathesis, and sinusitis. We present a case of a 55-year-old female with a history of chronic sinusitis who presented to the ED with a three-day history of left-sided periorbital swelling along with painful extraocular movements and markedly decreased visual acuity following a cross-country road trip through elevation. Contrast computed tomography scan of the orbits revealed a large extraconal collection in the subperiosteal space causing significant mass effect on the left globe, along with findings of diffuse sinonasal disease bilaterally. Intravenous antibiotics were started immediately and the patient underwent surgical incision and drainage of the subperiosteal space, where she was diagnosed with a spontaneous subperiosteal orbital hematoma secondary to chronic sinusitis. Within the literature, there are fewer than 20 case reports of orbital subperiosteal hematoma secondary to sinusitis. The purpose of this case report is to assist emergency physicians in considering the rare but potentially vision-threatening condition of spontaneous subperiosteal orbital hematoma within their differential diagnosis of patients with periorbital swelling and proptosis, as well as to provide an approach to management within the ED.

Parosteal osteosarcoma with a manifestation of subperiosteal low-grade central osteosarcoma.

We report the peculiar case of a parosteal osteosarcoma arising beneath the periosteum in a 12-year-old boy. He complained of difficulty in left knee flexion. Plain radiography showed a uniformly dense mineralized mass in the bone cortex and parosteal ossified nodules at the metaphysis and diaphysis of the left distal femur. Periosteal reaction was not evident. Uniquely, plain radiography had a smooth outline and revealed gradually thickening mass toward the center. Histologically, the tumor showed a proliferation of spindle-shaped cells with parallel-oriented dense bone trabeculae and hyaline cartilaginous tissue disclosing mild atypia. The periosteum was inverted along the polypoid mass, but there was no periosteum at the top. Immunohistochemically, the spindle cells, including those at the top of the polypoid mass, and cartilaginous cells were positive for MDM2 and CDK4. MDM2 gene amplification was detected in these cells by fluorescence in situ hybridization. Despite the peculiar feature of plain radiography, the lesion was diagnosed as parosteal osteosarcoma. This case report presents a case of parosteal osteosarcoma arising beneath the periosteum, although it is postulated to arise in the outer layer of the periosteum. The unique radiographic findings in this case suggest an association of parosteal osteosarcoma with vigorous bone growth before closure of the growth plate.

Canine calvarial subperiosteal hematomas are fluid to soft tissue attenuating mass-like lesions with smoothly marginated peripheral mineralization on CT.

Subperiosteal hematomas are accumulations of blood between a bone and the periosteum leading to elevation of the periosteum. When ossified they have a mineralized outer rim. For this retrospective, multi-institutional case series, medical records were searched to identify dogs that underwent CT for focal calvarial swellings noted acutely after trauma. A total of four dogs were included. Computed tomography images were reviewed for each case. The focal swellings had progressed in size during the weeks after the head trauma until the time of imaging. Findings in all cases included a fluid to soft tissue attenuating mass-like lesion with smoothly marginated peripheral mineralization. Diagnosis was confirmed in two cases by cytology and/or histopathology. Therefore, authors recommend that subperiosteal hematoma be included in the differential diagnosis list for dogs with these clinical and CT characteristics. Based on our review of the literature, this is the first report to describe the CT features of calvarial subperiosteal hematomas in dogs.

Pain, osteolysis, and periosteal reaction are associated with the STRYDE limb lengthening nail: a nationwide cross-sectional study.

Background and purpose - Observing serious adverse events during treatment with the Precice Stryde bone lengthening nail (NuVasive, San Diego, CA, USA), we conducted a nationwide cross-sectional study to report the prevalence of adverse events from all 30 bone segments in 27 patients treated in Denmark.Patients and methods - Radiographs of all bone segments were evaluated regarding radiographic changes in February 2021. We determined the number of bone segments with late onset of pain and/or radiographically confirmed osteolysis, periosteal reaction, or cortical hypertrophy in the junctional area of the nail.Results - In 30 bone segments of 27 patients we observed radiographic changes in 21/30 segments of 20/27 patients, i.e., 19/30 osteolysis, 12/30 periosteal reaction (most often multi-layered), and 12/30 cortical hypertrophy in the area of the junction between the telescoping nail parts. Late onset of pain was a prominent feature in 8 patients. This is likely to be a prodrome to the bony changes. Discoloration (potential corrosion) at the nail interface was observed in multiple removed nails. 15/30 nails were still at risk of developing complications, i.e., were not yet removed.Interpretation - All Stryde nails should be monitored at regular intervals until removal. Onset of pain at late stages of limb lengthening, i.e., consolidation of the regenerate, should warrant immediate radiographic examination regarding osteolysis, periosteal reaction, and cortical hypertrophy, which may be associated with discoloration (potential corrosion) of the nail. We recommend removal of Stryde implants as early as possible after consolidation of the regenerate.

MRI with state-of-the-art metal artifact reduction after total hip arthroplasty: periprosthetic findings in asymptomatic and symptomatic patients.

OBJECTIVES: To assess the spectrum of periprosthetic MRI findings after primary total hip arthroplasty (THA). METHODS: This multi-center cohort study analyzed 31 asymptomatic patients (65.7 ± 12.7 years) and 27 symptomatic patients (62.3 ± 11.9 years) between 6 months and 2 years after THA. 1.5-T MRI was performed using Compressed Sensing SEMAC and high-bandwidth sequences. Femoral stem and acetabular cup were assessed for bone marrow edema, osteolysis, and periosteal reaction in Gruen zones and DeLee and Charnley zones. Student t test and Fisher's exact test were performed. RESULTS: The asymptomatic and symptomatic groups showed different patterns of imaging findings. Bone marrow edema was seen in 19/31 (61.3%) asymptomatic and 22/27 (81.5%) symptomatic patients, most commonly in Gruen zones 1, 7, and 8 (p ≥ 0.18). Osteolysis occurred in 14/31 (45.2%) asymptomatic and 14/27 (51.9%) symptomatic patients and was significantly more common in Gruen zone 7 in the symptomatic group (8/27 (29.6%)) compared to the asymptomatic group (2/31 (6.5%)) (p = 0.03). Periosteal reaction was present in 4/31 asymptomatic (12.9%) and 9/27 symptomatic patients (33.3%) and more common in Gruen zones 5 and 6 in the symptomatic group (p = 0.04 and 0.02, respectively). In the acetabulum, bone marrow edema pattern was encountered in 3/27 (11.1%) symptomatic patients but not in asymptomatic patients (p ≥ 0.21). Patient management was altered in 8/27 (29.6%) patients based on MRI findings. CONCLUSIONS: Periprosthetic bone marrow edema is common after THA both in asymptomatic and symptomatic patients. Osteolysis and periosteal reaction are more frequent in symptomatic patients. MRI findings led to altered patient management in 29.6% of patients. KEY POINTS: • Bone marrow edema pattern was frequent in both asymptomatic and symptomatic patients after THA, particularly around the proximal femoral stem in Gruen zones 1, 7, and 8. • Osteolysis was significantly more frequent in symptomatic patients in Gruen zone 7. • Periosteal reaction occurred more frequently in symptomatic patients in Gruen zones 5 and 6.

It's time to recognize the perichondrium.

The perichondrium is a complex structure centered at the chondro-osseous junction of growing bones. It plays an important role in both normal skeletal development and in pathological conditions. This review illustrates the normal anatomy, function and imaging appearance of the perichondrium from fetal development to older childhood. The radiologic appearance of the perichondrium in skeletal trauma, infection and tumors in which it plays a role also are reviewed.

Temporal Evolution of Imaging Findings in Ossified Cephalohematoma.

BACKGROUND: Cephalohematoma is collection of blood between skull and periosteum that is confined by cranial sutures. Cephalohematomas usually resorb spontaneously within the first month of life; however, if it fails to resolve, ossified cephalohematoma may form. METHODS: Clinical archiving system and picture archiving and communication system were retrospectively reviewed for cases of birth-related cephalohematoma. Cases of ossified cephalohematomas identified on imaging were retrieved from this subset of patients. Cross-sectional imaging findings in patients with ossified cephalohematomas were evaluated for location, size of the hematoma, and contours of the inner lamella. RESULTS: Out of 115 cases of cephalohematoma, 7 cases had imaging findings consistent with ossified cephalohematoma. All ossified cephalohematomas were located parietally, with size ranging between 18 and 55 mm and the thickness of the outer rim of calcification ranging between 1.5 and 4.8 mm. The contour of inner lamella in relation to the surrounding normal cranial vault was normal in 5 cases, and inner lamella was depressed in 2 cases.Three patients had follow-up imaging available for demonstration of changes in ossified cephalohematoma. The first case was an 11 day-old boy with a cephalohematoma with no signs of calcification at the time of initial imaging. Follow-up at 2 months of age showed partial regression of hematoma cavity with marked calcification at the hematoma walls. The second case was a 3 month-old boy with ossified cephalohematoma at initial imaging. Follow-up imaging at 7 months of age showed almost total regression of hematoma cavity, and approximation of inner and outer lamella with increased thickness of the cranial vault. The third case was a 1 month-old boy with ossified cephalohematoma at initial imaging that totally resolved without residual increased bone thickness at 21-month follow-up. CONCLUSION: These 3 cases demonstrate the variability in temporal changes that may occur in ossified cephalohematomas.

Acute Megakaryoblastic Leukemia With Diffuse Periosteal Reaction of Bilateral Lower Extremities.

We report the case of a 3-year-old girl diagnosed with acute megakaryoblastic leukemia, who presented after >1 year of bilateral leg pain. At times the pain was severe enough to prevent ambulation, prompting visits to her primary care provider. However, it was not until acute respiratory failure occurred with subsequent hospitalization in the pediatric intensive care unit that severe anemia and thrombocytopenia were discovered and the diagnosis of acute myeloid leukemia was made. Bilateral lower extremity swelling was noted on admission and radiographs showed diffusely abnormal appearance of the long bones of her lower extremities with periosteal reaction and echogenic debris in the subperiosteal space, thought to represent leukemic cells. This case highlights the importance of recognizing atypical signs and symptoms of myelodysplastic syndrome progressing to acute leukemia in the context of abnormal bone pain and radiographic changes.

Error in the estimation of periosteal and endosteal contours from micro-CT scans for nonadult tibiae and humeri.

OBJECTIVES: This article summarized errors obtained by diverse techniques used for the derivation of cross-sectional contours in nonadult humeri and tibiae. MATERIALS AND METHODS: We analyzed cross-sectional contours in a total sample of 62 humeral and 75 tibial diaphyses in the age between birth and 12 years divided into three age groups. Long bone 35% (humeri) and midshaft (tibiae) cross-sections were taken on micro-CT images and analyzed by EPJMacro in FIJI. Properties were extracted from contours derived by manual, automatic, spline, and ellipse techniques. Agreement between techniques was assessed using manually extracted properties such as the true value using percent prediction error (%PE), reduced major axis regression, and ±95% limits of agreement. RESULTS: The lowest measurement errors were obtained for total areas, moderate errors for cortical areas and section moduli, and the highest errors for medullary areas for both bones. Derivation of humeral nonadult cross-sectional properties is less sensitive to the technique used for derivation of periosteal and endosteal contours, reaching mean %PEs below 5%. In contrast, tibial nonadult cross-sectional properties are more sensitive to the technique used and exceed 5% for some combinations. DISCUSSION: Automatic techniques provide reasonably high agreement with manually extracted contours for nonadult humeri but low agreement for tibiae. Semiautomatic approaches-spline and ellipse techniques-may reduce the error for all studied properties in tibiae, especially when combined with manually traced periosteal contours. The positive effect of the semiautomatic technique on measurement error is low for humeri.

Ultrasound Features of the Normal and Pathologic Periosteum.

Thickening and elevation of the periosteum from the underlying bone cortex, defined as a periosteal reaction, can be associated with several bone disorders. Although ultrasound (US) has limited possibilities in assessing bones, it can depict a periosteal reaction earlier than plain radiography, thus indicating underlying bone disorders. This pictorial essay aims to illustrate the normal and pathologic US appearances of the periosteum in both children and adults. Several disorders are discussed, such as pediatric bone trauma, infections and tumors, as well as trauma, overuse, including medial tibial stress syndrome, and finally certain seronegative spondyloarthropathies in adults. Whenever US depicts a periosteal reaction, a correlation with clinical and laboratory data is mandatory to differentiate different bone disorders. Computed tomography or magnetic resonance imaging must be performed when an infection or a tumor is suspected based on both US and the clinical presentation.

Type III Intraosseous Meningioma Invading Superior Sagittal Sinus and Skull Periosteum.

Type III intraosseous meningioma is a very rare type of meningioma with extracranial extension. Herein, the author reported a case of type IIIC intraosseous meningioma with invasion of the superior sagittal sinus and skull periosteum. A 67-year-old woman was admitted to our hospital due to a mass on the left frontoparietal region for 4 years. Magnetic resonance imaging showed a skull tumor with invasion of the superior sagittal sinus. After partial resection of the tumor, pathological and immunohistochemical staining revealed that the epithelial meningioma derived from skull involved the skull periosteum. There was no enlargement of residual parasagittal tumor after 1 year of follow-up. The intraosseous meningioma in the present case was a rare benign tumor with good prognosis after surgery.

Epinephrine auto-injector needle lengths: Can both subcutaneous and periosteal/intraosseous injection be avoided?

BACKGROUND: Epinephrine should be administered intramuscularly in the anterolateral aspect of the thigh. The length of the epinephrine auto-injector (EAI) needle should ensure intramuscular injection. OBJECTIVE: To discuss suitable EAI needle lengths based on ultrasound measurements related to weight. METHODS: The skin-to-muscle distance (STMD) and skin-to-bone distance (STBD) were measured by ultrasound in the mid-third of the anterolateral area of the right thigh when applying high pressure (8 lb; high-pressure EAI [HPEAI]) or low pressure (low-pressure EAI [LPEAI]) on the ultrasound probe. The study included 302 children and adolescents and 99 adults. The maximum and minimum STMD and the maximum and minimum STBD were estimated. RESULTS: Using HPEAIs, the risk of periosteal or intraosseous penetration was 32% in children weighing less than 15 kg. The risk of subcutaneous injection was 12% in adolescents and 33% in adults. With LPEAIs, there was no risk of periosteal or intraosseous injection and the risk of subcutaneous injections in adolescents and adults was lower at 2% and 10%, respectively. A new EAI for injection in small children would have no risk of periosteal or intraosseous injection but would have 71% chance of subcutaneous deposit of epinephrine. CONCLUSION: Common HPEAIs have a high risk of periosteal or intraosseous penetration in children and subcutaneous injections in overweight and obese adults. LPEAIs have some risk of subcutaneous injection in adults. HPEAIs with 0.1 mg of epinephrine and shorter needles have no risk of periosteal or intraosseous injection but have a high risk of subcutaneous deposit. For adult or overweight or obese patients, HPEAIs and LPEAIs should have longer needles. Future studies should focus on triggering pressures and variations in needle length.

Detection and characterization of the accessory mental foramen using cone-beam computed tomography.

OBJECTIVE: This study aimed to investigate the frequency and characteristics of accessory mental foramina (AMFs) and their bony canals in a selected Chinese population using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Reconstructed CBCT images of the mandible in 784 Chinese patients (305 males and 479 females) were retrospectively analysed to identify the AMF. The presence, dimension and location of the AMF as well as the origin and course of the associated bony canal were evaluated and classified. Variations in these characteristics were analysed according to gender, side and age. RESULTS: A total of 66 AMFs were found in 57 (7.3%) of the 784 patients. The frequency of AMFs was significantly influenced by gender and side of the mandible (p < .05). Most AMFs were located apically between apices of the first and second premolars. The high-position AMFs (above the mental foramen) accounted for 54.5% of the total. The mean horizontal and vertical diameters of the AMF were 1.38 ± 0.47 and 1.23 ± 0.37 mm, respectively. Two typical types of the bony canal leading to the AMF were identified according to their bifurcation site from the mandibular canal. Most bony canals originated from the anterior loop of the mental canal (56.1%) and coursed posterosuperiorly (36.3%). The mean length of the bony canals was 5.78 ± 2.31 mm. CONCLUSIONS: This study presents a considerable frequency of AMFs in a Chinese population. The high-position AMF and the associated bony canal coursing in the oblique upward direction appear frequently. Thus, clinicians should be alert to the presence of the AMF to avoid neurovascular complications especially when dental procedures require periosteum detachment and implant insertion in the mental region.

Plexiform neurofibroma causing an ossifying subperiosteal haematoma: a rare case in the tibia of an 11-year-old girl.

Ossifying subperiosteal haematoma is an exceedingly rare manifestation of Neurofibromatosis type 1 (NF-1). We report an interesting case of plexiform neurofibroma causing a rapidly growing tibial mass as a result of subperiosteal haemorrhage, in an 11-year-old girl with previously undiagnosed NF-1. This reflects a precursor of the more mature periosteal ossification seen in cases traditionally termed "subperiosteal cysts". A previously well young girl was referred by her general practitioner with an increasingly large, mildly tender, soft lump on the anterior aspect of her right tibia. Plain radiographs demonstrated soft tissue thickening overlying the anterior tibia, without appreciable periosteal ossification. Magnetic resonance imaging (MRI) illustrated a single central fluid-fluid level and periosteal elevation with saucerisation of the anterior tibial cortex and mild surrounding oedema. Histopathology revealed a large plexiform neurofibroma. Interestingly, this was associated with haemorrhagic change and a peripheral rim of florid reactive new bone formation. This unusual presentation was discussed at a multidisciplinary bone and soft tissue tumour meeting, where in combination with the clinical history of café au lait spots and positive family history, a consensus diagnosis of NF-1 was made. To date, there have only been limited case reports of this rare pathological process. In summary, this case report accounts an acute presentation of this rare osseous manifestation of NF-1, being the first to clearly demonstrate a timeline of subperiosteal haematoma with subsequent subperiosteal bone proliferation. The clinical reasoning and radiological features for such a presentation are also described.