A 36 year old female, born with a myelomeningocele, presented with a paralysis of the right facial nerve.
The patient was born with a myelomeningocele. The patient has severe complications of the neural defect, including mental retardation, paraplegia and urinary incontinence. Because of a non-communicating hydrocephalus, she was treated with a ventriculoperitoneal shunt in her early childhood. Recently she developed paralysis of the right facial nerve. A CT examination of the brain was performed to exclude a central cause of the paralysis.
The ventriculoperitoneal shunt was correctly positioned within the right lateral ventricle. There was hydrocephalus, microcephaly and descent of the cerebellar tonsils within an enlarged foramen magnum (not shown). There were no imaging signs of a central paralysis of the right facial nerve (bleeding, ischemia, mass lesions). The most remarkable finding on the examination is the diffuse thickening of the calvarian bone. This thickening is most pronounced at the frontal bone (thickening up to 2.4 cm), but also affects the parietal, temporal and occipital bones. The other bones are not involved. The thickening itself consists of a concentrically layered expansion of the diploe. The pattern of calvarian thickening and the history of a ventriculoperitoneal shunt placed in the childhood suggest the diagnosis of hyperostosis cranii ex vacuo. This condition could not be linked with the development of a paralysis of the facial nerve.
Hyperostosis cranii ex vacuo can be defined as the diffuse thickening of the diploe of the calvarian bones. The calvarian bones consist of the frontal, parietal, temporal and occipital bones. The other skull bones are not affected. The thickening is contributed to a widening of the diploe, as in our case.
The disease was first described in 1965 by Emery in a case of a patient with ventricular shunting. Since then, a few dozen of cases have been published. In most of these cases, the patients were successfully treated for hydrocephalus in their childhood with a ventricular shunt. Another case is described after choroid plexus coagulation and one article suggests the phenomenon to be more general pointing to a relationship between dynamic changes in brain size and skull thickness.
In one series of 230 patients operated for hydrocephalus between 1938-1967, 7 cases were found after a follow up between 3 years and 2 months and 8 years and 6 months, thus leading to an incidence of 3% in patients treated for hydrocephalus.
A relationship with the severity of hydrocephalus, microcephaly, early closure of the sutures and intracranial hypotension has been suggested. In case of a normal development of the skull, outward pressure by the cranial content stimulates intramembranous bone growth along the cranial sutures. Due to chronic intracranial hypotension, the growth of the calvarian bone seems to occur at the inner table, leading to a widening of the diploe.
Differential diagnosis of thickening of the calvarian bones includes healed rickets, severe longstanding anaemia, thalassemia, craniometaphyseal dysplasia, Paget's disease, fibrous dysplasia and hyperostosis frontalis interna.
Hyperostosis cranii ex vacuo
CT axial and coronal images show:
1. Bilateral ventricles are noticeably enlarged compared to previous examinations, suggesting a history of hydrocephalus or abnormal intracranial pressure. A cerebrospinal fluid shunt is visible within the ventricles.
2. Thickening of the calvarial diploic space is observed, especially in the vertex, frontal bone, parietal bone, and portions of the temporal bone. The widened diploic space (between the inner and outer tables) appears uniformly thickened.
3. The inner and outer skull tables remain structurally intact, with no obvious bony destruction or focal space-occupying lesions.
4. The bony configuration in the region of the right facial nerve canal appears largely normal, with no significant evidence of bony destruction or stenotic lesions. However, the possibility of chronic changes exerting pressure on the nerve cannot be ruled out.
Based on the patient's history of myelomeningocele surgery and ventricular shunt placement, as well as pronounced calvarial thickening between the inner and outer skull tables, consider the following:
Taking into account the patient’s early life history of neural tube defect (myelomeningocele) and previous cerebrospinal fluid shunt placement, along with the current imaging findings of generalized, symmetrical thickening of the calvaria, the presentation is consistent with “Hyperostosis cranii ex vacuo.” This condition is typically associated with chronic reductions in brain volume and long-term mildly reduced intracranial pressure, causing compensatory thickening of the skull plates.
1. Treatment Strategy:
- In cases of purely imaging-based changes with stable disease and no significant fluctuations in intracranial pressure, regular follow-up and observation are advised.
- If there is suspicion of shunt malfunction or evidence of worsening neurological symptoms (e.g., increased intracranial pressure, persistent headache, nausea, vomiting), evaluation of the shunt function should be considered, followed by repair or replacement if necessary.
- If right-sided facial nerve palsy is suspected to be related to local bony changes or other causes, further electrophysiological examination of the facial nerve is recommended to rule out reversible damage, with microsurgical or endoscopic decompression to be considered when indicated.
2. Rehabilitation and Exercise Prescription:
- Given the patient’s background of myelomeningocele, special attention should be paid to comprehensive training for the lower extremities and lumbar region, avoiding excessive load-bearing.
- Initially, implement low-intensity aerobic exercise, such as walking on level ground or aquatic walking, for 15–20 minutes per session, 3 times per week. Monitor the patient’s response post-exercise, gradually extending each session up to 30 minutes as tolerated.
- As endurance improves, progress to moderate-intensity stationary cycling or interval walking for 20–30 minutes per session, 3–4 times per week.
- Incorporate suitable muscle strengthening exercises (e.g., resistance band workouts), focusing on the core and lower limb muscles 2–3 times per week, while avoiding high-intensity loads to protect spinal stability.
- Range-of-motion and Neurological Rehabilitation: For right-sided facial nerve impairment, under professional guidance, include facial muscle stretching, massage, and facial expression training to reduce muscle atrophy and sequelae from nerve damage.
- Throughout the rehabilitation process, adjust exercise intensity based on subjective feedback and objective measures (e.g., blood pressure, heart rate, respiration) to ensure safety.
Disclaimer: This report is based solely on the provided medical history and imaging data and does not replace a clinical consultation or professional medical advice. Please follow the guidance of specialized physicians for specific diagnoses and treatments.
Hyperostosis cranii ex vacuo
