Stroke-like migraine attacks after radiation therapy (SMART) syndrome

A 52-year-old man with history of metastatic testicular seminoma and adjuvant brain irradiation therapy (21 years ago) with recurrent seizures during the last 11 years presented with aphasia, altered mental status of consciousness and hemiparesis of the right upper and right lower limb, with referred symptoms’ initiation 6 days ago.

Cortical thickening of the parieto-temporo–occipital regions of the left cerebral hemisphere associated with mild abnormal high signal intensity of the affected cortex on T2 and FLAIR images (Figures 1, 2), intense gyriform post-gadolinium enhancement and coexistent leptomeningeal enhancement (Figure 3). Hyperperfusion of the affected areas was also seen on MR perfusion images (Figure 4). Follow-up brain MRI after 6 months demonstrated complete resolution of the cortical oedema, normal perfusion and absence of gadolinium enhancement of the affected areas (Figures 5, 6).

SMART syndrome is a rare delayed complication following cranial irradiation therapy in patients with central nervous system malignancies or brain metastatic disease. The syndrome typically presents as recurrent complex migraine attacks with reversible, unilateral focal neurologic signs such as hemiparesis, seizures and aphasia [1, 2]. Patients typically present with SMART syndrome between 1 to 37 years after cranial irradiation therapy. The exact mechanisms of SMART syndrome remain unknown; however, it has been associated with cerebral hyperexcitability, intrinsic impairment of the autoregulatory mechanisms, vascular endothelial damage and impaired blood-brain barrier integrity as a consequence of irradiation damage [2]. Development of the SMART syndrome has been correlated to a radiation dose of at least 50 Gy [4]. The diagnosis of SMART syndrome involves the combination of both clinical semiology and brain MRI specific findings. Imaging hallmarks of SMART syndrome include; prominent unilateral cortical thickening (defined as gyriform abnormal high signal intensity on T2 and FLAIR sequences) associated with mild mass effect due to oedema, intense post-gadolinium gyral enhancement and hyperperfusion of the affected areas [3, 4, 5]. The characteristic gyriform cortical enhancement typically develops within 2–7 days and usually resolves in 13–35 days [1]. All these imaging findings are usually confined to the irradiated areas and preferentially in the posterior areas of the brain parenchyma. Typically the subcortical and deep white matter structures lack involvement [1]. Restricted diffusion or mild leptomeningeal enhancement may or may not be seen [3, 4]. Imaging findings may appear 2–7 days after symptoms’ onset and typically resolve after 2–5 weeks [3]. As a permanent sequelae of SMART syndrome, cortical laminar necrosis may be seen [3]. Quite common accessory imaging findings include multiple magnetic susceptibility foci compatible with cavernous malformations (>5 mm) and/or microbleeds (<5 mm) as well as imaging findings consistent with leukoencephalopathy, both as sequelae of prior radiotherapy [2, 3].