A 14-year-old male patient presented to the department of maxillofacial surgery for further work-up of a radiolucent lesion within the left mandible, which was incidentally found on a routine panoramic radiograph. There is a history of trauma from a previous fall on the chin 5 years prior to the current admission.
Cone Beam Computed Tomography (CBCT) showed a unilocular, well-defined radiolucent lesion with thin sclerotic margins in the body of the mandible (Fig. 1A, B). The lesion had a slight polylobular morphology and caused thinning of the buccal and lingual cortex. Although there was an intimate relationship with the apex of tooth 43, erosion was absent (Fig. 2B).
Fat-suppressed (FS) T2-weighted MR images demonstrated a hyperintense, well-delineated lesion with slight polylobular margins in the median aspect of the mandible body (Fig. 3A,3B).
Coronal T1-weighted MR images before (Fig. 3C) and after (Fig. 3D, 3E) intravenous gadolinium contrast injection showed subtle peripheral rim enhancement.
Idiopathic Bone Cavity (IBC) or Simple Bone Cyst (SBC) is a benign intraosseous cavity of unknown aetiology, frequently observed among young adults [1-5].
IBC is a pseudocyst as it lacks epithelial lining and is either empty or filled with serous or sanguineous fluid and is therefore sometimes designated as a “haemorrhagic bone cyst”. IBC is also referred to as Traumatic Bone Cyst because association with trauma has been reported in some cases with symptoms including pain, tooth sensitivity and paraesthesia. However, in most cases, the lesion is asymptomatic with inapparent traumatic events and is incidentally discovered on radiographs performed for dental purposes [1,4].
It is important to distinguish IBC from more worrisome odontogenic lesions. The main imaging modalities are panoramic radiography and (CBCT), and in selected cases, Magnetic Resonance Imaging (MRI) may be helpful for further characterisation and additional information regarding soft tissue extension [2,3,4].
The typical radiographic appearance of IBC is a radiolucent and unilocular lesion with well-circumscribed borders, expanding between the roots of teeth, with no or slight cortical expansion. The corpus of the mandible is the most frequently affected area. Despite its potential expansile nature, teeth displacement or root resorption are rare, and the lamina dura is usually intact or only partly disrupted [1-4].
(CB)CT scan usually demonstrates a central, well-defined, mildly expansile or nonexpansile, thin-walled lytic lesion, with little or no marginal sclerosis.
MRI usually confirms the cystic nature of the lesion by showing its fluid content. Fluid-fluid levels are rarely seen in non-complicated lesions. However, fractured IBCs may contain blood products and fluid-fluid levels. On MRI, the lesion shows low signal intensity on T1-weighted images, and high signal intensity on T2-weighted or Short Tau Inversion Recovery (STIR) images [1-4].
The above described radiological features are pathognomonic and usually sufficient to establish the diagnosis of IBC without any need for further invasive assessment. However, in rare cases, clinical imaging is in conclussion necessitating histopathological examination of biopsy specimens to reach a final diagnosis and distinguish the lesion from other radiolucent lesions of the jaws [1,2,4]. Histological examination in our case revealed the absence of epithelial lining.
IBC is mostly a self-limiting benign lesion that heals spontaneously after skeletal maturity. Therefore, a short-term follow up would mostly be the best approach and unnecessary extensive surgical intervention should be avoided. Symptomatic cases could warrant a limited exploration and curettage with appropriate follow-up. The overall prognosis is excellent [1-5].
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Idiopathic Bone Cavity
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Based on the provided panoramic film, lateral film, and subsequent CT and MRI images, there is a single radiolucent lesion with clear boundaries observed in the left mandibular body region.
On conventional X-ray and CT images, this lesion appears round or oval with well-defined edges. The local cortical bone is slightly thinned but shows no obvious destruction or significant expansion. The shape of the tooth roots remains intact, and there is no obvious resorption or loosening of the adjacent teeth. The local bone exhibits a cavity-like change.
On MRI images, the lesion shows low signal intensity on T1-weighted sequences and high signal intensity on T2-weighted and STIR sequences, suggesting fluid content within the lesion. No obvious soft tissue mass or infiltration was noted. Overall, the findings are consistent with a simple cystic (cavity) lesion.
Based on the patient’s age (14 years), a history of no significant symptoms or only mild discomfort, a history of previous trauma, and the typical radiographic appearance of a cavity-like lesion—after excluding odontogenic cysts and benign tumors—the most likely diagnosis is:
Simple Bone Cyst (Idiopathic Bone Cavity / Traumatic Bone Cyst).
If further confirmation is necessary, surgical exploration or biopsy may reveal an empty cavity without epithelial lining, distinguishing it from other cystic or neoplastic lesions.
Considering the benign and self-limiting nature of a Simple Bone Cyst (IBC/SBC), a conservative approach with regular follow-up is often adopted if there are no significant symptoms or functional disabilities. Surgical intervention (e.g., curettage) may be considered if the lesion is large, symptomatic, or shows signs of expansion upon follow-up.
1. Conservative Follow-up and Observation
If the patient has no obvious discomfort or functional impairment, imaging follow-up every 3–6 months is recommended to monitor for any changes in the lesion size or surrounding bone. Many simple bone cysts remain stable or heal as skeletal maturity is reached.
2. Surgical Management
If the patient experiences pain, marked thinning of the bone, or any suspicion that the lesion is progressively enlarging, limited surgical exploration can be performed. If necessary, curettage of the lesion can help promote bone healing. Postoperative follow-up should continue to monitor local bone repair.
3. Rehabilitation and Exercise Prescription
For patients with large cystic cavities or significant symptoms, it is advisable to avoid high-impact exercises (e.g., running, jumping) in the early postoperative period or when bone quality is compromised. Gradually resume activity as the local bone stabilizes. Follow the FITT-VP principles as below:
This report is based solely on the limited information and imaging findings provided. It serves as a reference and does not replace in-person consultations or professional medical advice. If there are any concerns or worsening of symptoms, it is advised to seek hospital-based examination and treatment promptly.
Idiopathic Bone Cavity
