Rasmussen encephalitis
Updates to Article Attributes
Rasmussen encephalitis, also known as chronic focal encephalitis, is a chronic inflammatory disease of unknown origin, usually affecting one brain hemisphere.
It is not to be confused with a Rasmussen aneurysm.
Epidemiology
Most cases (85% cases) occur in children under the age of 10 years 1. However, detection in adults is increasing with routine MRI investigations for intractable seizures 5.
Clinical presentation
Patients frequently have episodes of epilepsia partialis continua or generalised status epilepticus, although thisthe latter is less common. The seizures are intractable despite aggressive medical management 1.
Apart from seizures, the patient may have hemiparesis and speech disturbances, as well as hemianopia (pertaining to unilateral cerebral involvement). Mental deterioration over time may also be seen, especially in a patient presenting later in adolescence.
Pathology
Pathologic features are similar to viral encephalitis, with lymphocytes aroundsurrounding round cells and diffuse proliferation of microglia. However, later spongiform degeneration and cortical atrophy sets set in.
The observed inflammatory changes in Rasmussen encephalitis include perivascular cuffing, microglial nodules, T-lymphocytic infiltration gliosis, meningeal inflammation, and neuronal injury or loss 9,10.
An autoimmune mechanism has also been proposed describing antibodies against theGluR3 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor in a few patients 11.
The exact cause of the disease is unknown. However, various viral (SSPE-like, EBV or CMV) or inflammatory episodes have been implicated by different authors 3,4,6.
Radiographic features
Radiographic features are usually isolated to a single hemisphere,; however, bilateral Rasmussen encephalitis has also been rarely described in numerous case reports 12-14.
CT
CT may not show any specific feature in early imaging; however, patchy hypodense attenuation areas (similar to viral encephalitis) may be seen. The late-stage disease may show unilateral cortical atrophy. CT perfusion may show decreased cerebral blood flow (CBF) 1.
MRI
Atrophy is typically earliest appreciated in the ipsilateral caudate nucleus, before atrophy and signal changes are appreciated more generally in the hemisphere. Signal characteristics include:
-
T1: unilateral cortical atrophy with ex
-vacuovacuo ventricular dilatation 15 - T2: hyperintense signal areas in the affected hemisphere 15
- DWI/ADC: restricted diffusion may be seen in altered signal areas 15
- T1 C+ (Gd): no significant post-contrast enhancement 15
Treatment and prognosis
Treatment with high-dose methylprednisolone and intravenous immunoglobulin has been positive, further supporting the autoimmune nature of the disease 16,17. Anti-seizure medications have a limited symptomatic role 17.
Functional hemispherectomy is the only definitive treatment in refractory cases, withwhich resolves seizure activity or significantly decreases seizure frequency in most patients having either no or less frequent seizures 16.
History and etymology
It was first described by American neurologist Theodore Brown Rasmussen (1910-2002) in 1958 2.
Differential diagnosis
General imaging differential considerations include:
- Dyke-Davidoff-Masson syndrome
- Sturge Weber syndrome
- unilateral megalencephaly
-
hemiconvulsion-hemiplegia epilepsy syndrome (HHE)
- HHE syndrome usually shows a seizure
free-free interval of months to years from initial presentation 7,8
- HHE syndrome usually shows a seizure
-<p><strong>Rasmussen encephalitis</strong>, also known as <strong>chronic focal encephalitis</strong>, is a chronic inflammatory disease of unknown origin, usually affecting one brain hemisphere.</p><p>It is not to be confused with a <a href="/articles/rasmussen-aneurysm">Rasmussen aneurysm</a>.</p><h4>Epidemiology</h4><p>Most cases (85% cases) occur in children under the age of 10 years <sup>1</sup>. However, detection in adults is increasing with routine MRI investigations for intractable seizures <sup>5</sup>.</p><h4>Clinical presentation</h4><p>Patients frequently have episodes of epilepsia partialis continua or generalised <a href="/articles/status-epilepticus">status epilepticus</a>, although this is less common. The seizures are intractable despite aggressive medical management <sup>1</sup>.</p><p>Apart from seizures, the patient may have hemiparesis and speech disturbances, as well as hemianopia (pertaining to unilateral cerebral involvement). Mental deterioration over time may also be seen, especially in a patient presenting later in adolescence.</p><h4>Pathology</h4><p>Pathologic features are similar to viral encephalitis, with lymphocytes around round cells and diffuse proliferation of microglia. However, later spongiform degeneration and cortical atrophy sets in.</p><p>The observed inflammatory changes in Rasmussen encephalitis include perivascular cuffing, microglial nodules, T-lymphocytic infiltration gliosis, meningeal inflammation, and neuronal injury or loss <sup>9,10</sup>.</p><p>An autoimmune mechanism has also been proposed describing antibodies against<sup> </sup>GluR3 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor in a few patients <sup>11</sup>.</p><p>The exact cause of the disease is unknown. However, various viral (SSPE-like, EBV or CMV) or inflammatory episodes have been implicated by different authors <sup>3,4,6</sup>.</p><h4>Radiographic features</h4><p>Radiographic features are usually isolated to a single hemisphere, however bilateral Rasmussen encephalitis has also been rarely described in numerous case reports <sup>12-14</sup>. </p><h5>CT</h5><p>CT may not show any specific feature in early imaging; however, patchy hypodense attenuation areas (similar to viral encephalitis) may be seen. The late-stage disease may show unilateral cortical atrophy. CT perfusion may show decreased cerebral blood flow (CBF) <sup>1</sup>.</p><h5>MRI</h5><p>Atrophy is typically earliest appreciated in the ipsilateral caudate, before atrophy and signal changes are appreciated more generally in the hemisphere. Signal characteristics include:</p><ul>- +<p><strong>Rasmussen encephalitis</strong>, also known as <strong>chronic focal encephalitis</strong>, is a chronic inflammatory disease of unknown origin, usually affecting one brain hemisphere.</p><p>It is not to be confused with a <a href="/articles/rasmussen-aneurysm">Rasmussen aneurysm</a>.</p><h4>Epidemiology</h4><p>Most cases (85% cases) occur in children under the age of 10 years <sup>1</sup>. However, detection in adults is increasing with routine MRI investigations for intractable seizures <sup>5</sup>.</p><h4>Clinical presentation</h4><p>Patients frequently have episodes of epilepsia partialis continua or generalised <a href="/articles/status-epilepticus">status epilepticus</a>, although the latter is less common. The seizures are intractable despite aggressive medical management <sup>1</sup>.</p><p>Apart from seizures, the patient may have hemiparesis and speech disturbances, as well as hemianopia (pertaining to unilateral cerebral involvement). Mental deterioration over time may also be seen, especially in a patient presenting later in adolescence.</p><h4>Pathology</h4><p>Pathologic features are similar to <a title="Viral encephalitis" href="/articles/viral-encephalitides">viral encephalitis</a>, with lymphocytes surrounding round cells and diffuse proliferation of <a title="Microglia" href="/articles/microglia">microglia</a>. However, later <a title="Spongiform degeneration of white matter" href="/articles/canavan-disease">spongiform degeneration</a> and <a title="cortical atrophy" href="/articles/cerebral-atrophy">cortical atrophy</a> set in.</p><p>The observed inflammatory changes in Rasmussen encephalitis include perivascular cuffing, microglial nodules, T-lymphocytic infiltration gliosis, meningeal inflammation, and neuronal injury or loss <sup>9,10</sup>.</p><p>An autoimmune mechanism has also been proposed describing antibodies against the<sup> </sup>GluR3 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor in a few patients <sup>11</sup>.</p><p>The exact cause of the disease is unknown. However, various viral (SSPE-like, EBV or CMV) or inflammatory episodes have been implicated by different authors <sup>3,4,6</sup>.</p><h4>Radiographic features</h4><p>Radiographic features are usually isolated to a single hemisphere; however, bilateral Rasmussen encephalitis has also been described in numerous case reports <sup>12-14</sup>. </p><h5>CT</h5><p>CT may not show any specific feature in early imaging; however, patchy hypodense attenuation areas (similar to viral encephalitis) may be seen. The late-stage disease may show unilateral cortical atrophy. CT perfusion may show decreased <a title="Cerebral blood flow (CBF)" href="/articles/cerebral-blood-flow-cbf">cerebral blood flow</a> (CBF) <sup>1</sup>.</p><h5>MRI</h5><p>Atrophy is typically earliest appreciated in the ipsilateral <a title="Caudate nucleus" href="/articles/caudate-nucleus">caudate nucleus</a>, before atrophy and signal changes are appreciated more generally in the hemisphere. Signal characteristics include:</p><ul>
-<strong>T1:</strong> unilateral cortical atrophy with ex-vacuo ventricular dilatation <sup>15</sup>- +<strong>T1:</strong> unilateral cortical atrophy with <a title="Hydrocephalus ex vacuo" href="/articles/hydrocephalus-ex-vacuo">ex vacuo</a> ventricular dilatation <sup>15</sup>
-</ul><h4>Treatment and prognosis</h4><p>Treatment with high-dose methylprednisolone and intravenous immunoglobulin has been positive, further supporting the autoimmune nature of the disease <sup>16,17</sup>. Anti-seizure medications have a limited symptomatic role <sup>17</sup>.</p><p>Functional hemispherectomy is the only definitive treatment in refractory cases, with most patients having either no or less frequent seizures <sup>16</sup>.</p><h4>History and etymology</h4><p>It was first described by American neurologist <strong>Theodore Brown Rasmussen</strong> (1910-2002) in 1958 <sup>2</sup>.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>- +</ul><h4>Treatment and prognosis</h4><p>Treatment with high-dose methylprednisolone and intravenous immunoglobulin has been positive, further supporting the autoimmune nature of the disease <sup>16,17</sup>. Anti-seizure medications have a limited symptomatic role <sup>17</sup>.</p><p>Functional hemispherectomy is the only definitive treatment in refractory cases, which resolves seizure activity or significantly decreases seizure frequency in most patients <sup>16</sup>.</p><h4>History and etymology</h4><p>It was first described by American neurologist <strong>Theodore Brown Rasmussen</strong> (1910-2002) in 1958 <sup>2</sup>.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>
-<a href="/articles/hemiconvulsion-hemiplegia-epilepsy-syndrome">hemiconvulsion-hemiplegia epilepsy syndrome</a> (HHE)<ul><li>HHE syndrome usually shows a seizure free interval of months to years from initial presentation <sup>7,8</sup>- +<a href="/articles/hemiconvulsion-hemiplegia-epilepsy-syndrome">hemiconvulsion-hemiplegia epilepsy syndrome</a> (HHE)<ul><li>HHE syndrome usually shows a seizure-free interval of months to years from initial presentation <sup>7,8</sup>
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