American Journal of Neuroradiology

Case of the Week

Section Editors: Matylda Machnowska¹and Anvita Pauranik²
¹University of Toronto, Toronto, Ontario, Canada
²BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada

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July 11, 2024

Linear Scleroderma

Background:
- Morphea is a form of localized scleroderma that affects mostly the skin, but other organ lesions could also be associated. It is a rare disease with an estimated annual incidence of 2.7 per 100,000, with a prevalence of 50 per 100,000. Active morphea lesions are characterized by erythema and induration, and notably, most lesions have an insidious course and are asymptomatic. Inactive lesions show sclerosis and atrophy of the epidermis, dermis, and subcutaneous tissues, occasionally involving the bone below.
- Patients may experience serious aesthetic problems, tissue atrophy, functional disabilities, as well as muscular and neurologic complications. Hence, early diagnosis of the active disease, staging, and deciding on a treatment are very important. The clinical presentation of morphea differs according to its subtype, degree of involvement, and stage of evolution.
- Linear scleroderma, also known as scleroderma "en coup de sabre," is a subset of localized scleroderma, which is more frequent in pediatric patients. It is classically characterized by a lateralized linear atrophic band involving soft tissues of the frontoparietal scalp and subjacent thinned calvaria, associated with ipsilateral focal brain abnormalities. Some reported cases also present other organ involvement with rheumatologic and ophthalmologic symptoms. "En coup de sabre" is a French expression that alludes to the appearance of a frontoparietal lesion as if the patient had been struck by a saber.
- Linear scleroderma may coexist with progressive facial hemiatrophy, which is known as Parry-Romberg syndrome.
- The etiology of linear scleroderma is not well understood. There is evidence suggesting an autoimmune origin of this disease. In a few reported cases with histologic analysis, the findings include vasculitis, inflammatory infiltrate, gliosis, leptomeningeal band-like sclerosis, thickened blood vessel walls, and intraparenchymal calcifications, all of which suggest a chronic inflammatory process.
- The diagnosis of linear scleroderma is made based on the clinical characteristics of the cutaneous and soft tissue findings. A contrast-enhanced MRI is imperative due to the disease's association with brain lesions.
- There are no laboratory tests diagnostic for linear scleroderma. However, patients may test positive for antinuclear antibodies, anti-single-stranded DNA antibodies, and rheumatoid factor.

Clinical Presentation:
- Lateralized linear atrophic band involving soft tissues of the frontoparietal scalp
- Neurologic symptoms usually appear after the development of the skin lesion. Seizures are the most frequent symptom. Other symptoms include focal neurologic deficits and movement disorders, which can be secondary to brain lesions, trigeminal neuralgia, masticatory spasms, behavioral changes, or progressive intellectual deterioration due to cerebral hemiatrophy.

Key Diagnostic Features:
- The band of soft tissue atrophy in the frontoparietal region is visible on brain CT or MRI. The underlying bone can also be affected.
- Neuroimaging findings in the cerebral hemisphere are typically ipsilateral to the skin lesions.
- Calcifications are frequent findings, and they typically involve the basal ganglia, thalami, dentate nuclei, and less often subcortical white matter.
- MRI usually exhibits T2 hyperintensities, mostly in the subcortical white matter, but also in the corpus callosum, deep grey nuclei, and brainstem.
- Cerebral atrophy is generally focal and subtle, but it can be more extensive, always affecting the ipsilateral cerebral hemisphere. However, earlier in the course, mild cortical swelling may be seen with sulcal effacement, and an abnormal gyral pattern (as seen in our patient).
- An enhanced MRI of control can be done to evaluate the progression of the lesions in the brain. However, the disease usually has a benign course.

Differential Diagnosis:
The main distinctions are drawn with pediatric pathologies that affect the gray and white matter of one cerebral hemisphere.
- Rasmussen encephalitis: This is a chronic focal encephalitis with inflammatory findings of unknown origin that typically affects one cerebral hemisphere. Atrophy is usually first noticed in the ipsilateral caudate nucleus, before it becomes more evident throughout the hemisphere. Signal characteristics include unilateral cortical atrophy with ex vacuo ventricular dilation and areas of T2 hyperintense signal in the affected hemisphere, often with restricted diffusion. There is often no postcontrast enhancement.
- Hemimegalencephaly: This is a rare congenital disorder involving cortical formation with hamartomatous overgrowth of all or part of a cerebral hemisphere. Typical features include enlarged lateral ventricle size, shallow sulci, enlarged gyri, thickened calvaria, contralateral displacement of the posterior falx, and white matter calcification. Also, there is an association with developmental venous anomalies. Macrocephaly may be present.