Intramedullary spinal cord metastases

Findings

Figure 1: Sagittal T1 weighted image shows focal expansion of the cord substance in the region of the upper dorsal vertebrae (T3 and T4). The area is isointense to the cord.
Figure 2 and Figure 3: Sagittal T2 weighted and STIR images show a hyperintense lesion involving the dorsal spinal cord with edema, seen at its rostral and caudal ends. Incidentally seen is a hemangioma (Figure 1 and Figure 2) involving the T7 vertebral body.

Figure 4 and Figure 5: Post contrast axial and sagittal T1 weighted images show almost homogeneous enhancement in the lesion. Incidentally seen are pleural effusion (Figure 5) and pulmonary metastasis (Figure 5).


Diagnosis: Intramedullary spinal cord metastases (ISCM)


The most common neurological complications of breast cancer are brain metastases and spinal cord compression. In most instances spinal cord compression is caused by extra-dural soft tissue masses, however ISCM is a rare and a distinct diagnostic possibility.

ISCM is an unusual presentation of systemic malignancies. Close to 50% of all ISCMs arise from primary lung tumors, with small cell carcinoma being the most common. The remainder originate from primary cancers of the breast, colon, melanoma, lymphoma, and kidney. ISCMs are typically solitary and extend over a length of 2-3 vertebral segments.

The clinical manifestations of metastatic intramedullary spinal cord tumors are typically back pain, paresthesia, paraparesis, spasticity of the lower extremities, and autonomic dysfunction.

Magnetic resonance imaging is considered the gold standard for the diagnosis of tumors affecting the spinal cord. The typical ISCM seen on MRI is a small, isolated, oval-shaped lesion with or without slight deformation of the spinal cord profile. It is isointense on T1-weighted images with a nodular contrast enhancement and a pencil-shaped hyperintensity on T2-weighted sequences, most frequently extending proximal to the lesion. Cysts are rare, in contrast to primary intramedullary neoplasm.

External beam radiation with or without concomitant corticosteroids has been the most effective method of treating ISCM. In a small group of selected patients, surgical resection seems be a reasonable option, especially in cases presenting with previously undiagnosed or limited primary tumors and rapid neurologic deterioration. Also, when the primary tumor is well known to be radioresistant, as in the case of melanoma or renal cell carcinoma, surgical decompression or subtotal resection would be indicated.

Patients with ISCM have a very short life expectancy; their median survival is 3 to 4 months from the time of diagnosis. Those with breast cancer as the primary source of ISCM, tend to do better than other types of cancer; their median survival is 13 months.

Chronic progressive external ophthalmoplegia

Findings

The extraocular muscles are atrophic and to some degree show fatty replacement. No abnormal enhancement is present. The globes are intact bilaterally. The intraorbital fat appears slightly increased. There is bilateral orbital proptosis with both globes anterior to the interzygomatic line.


Diagnosis: Chronic progressive external ophthalmoplegia


Key points

Chronic progressive external ophthalmoplegia (CPEO) is characterized by slowly progressive paralysis of the extraocular muscles.
Mitochondrial myopathy usually associated with skeletal muscle weakness.
Presents with bilateral, symmetrical, progressive ptosis, followed by ophthalmoparesis months to years later.

Kearns-Sayre syndrome: Related mitochondrial myopathy with CPEO, onset before age 20 years, pigmentary retinopathy, and at least one of the following: cardiac conduction defects, CSF protein of greater than 100 mg/dL, and/or cerebellar syndrome.
KSS can include mental retardation, hearing loss, seizures, short stature, delayed puberty, and various endocrine disorders.
Frequency: Rare. Males=Females.

Imaging studies: MRI, CT, and ultrasound may show thin, symmetrical extraocular muscles in CPEO, in contrast to enlarged extraocular muscles sometimes seen with Graves disease.
Those with KSS and CPEO display a wide spectrum of MRI findings, including normal brain, diffuse atrophy, and T2 prolongation in subcortical cerebral white matter, cerebellar white matter, globi pallidi, thalami, and substantia nigra.
Diagnosis: Muscle biopsy is definitive test but PCR also shown to be conclusive.

Mesial temporal sclerosis with infarct of the parahippocampal gyrus

Findings

There is expansion and abnormal FLAIR and T2 signal within the right hippocampal formation and parahippocampal gyrus. There is diffusion restriction of the parahippocampal gyrus.


Diagnosis: Mesial temporal sclerosis with infarct of the parahippocampal gyrus


Discussion

Mesial temporal sclerosis (MTS) is a poorly understood phenomenon involving atrophy and sclerosis of the hippocampus and adjacent structures, namely, the amygdala, parahippocampal gyrus, and uncus. MTS may be acquired in the setting of prolonged febrile seizures, status epilepticus, or cerebral ischemia. Histopathology demonstrates neuronal loss and fibrillary gliosis. There has been controversy regarding whether MTS is the cause or the result of temporal lobe epilepsy. However, there is a clear connection since the majority of temporal lobe resection specimens done for temporal lobe epilepsy demonstrate MTS. Approximately 15% of temporal lobe resection specimens exhibit both MTS and another lesion such as cortical dysplasia. Approximately 25% of patients are successful with medical therapy. The patient presented here had longstanding seizures and had a recent seizure which resulted in acute infarction of the parahippocampal gyrus. This may result from seizure related hypoxemia.


Radiologic overview

MR demonstrates increased T2 signal as a result of neuronal loss and gliosis. Increased FLAIR signal is also seen but caution is necessary as limbic structures all demonstrate slight hyper intensity on FLAIR. Magnetic resonance spectroscopy can be used to evaluate MTS since interictal N- acetyl aspartate (NAA) is reduced in the ipsilateral temporal lobe compared with the uninvolved temporal lobe. Lactate and lipid peaks may be increased if scanned within 24 hours of seizure. Nuclear medicine studies demonstrate reduced activity if injected interictally and increased activity if injected ictally.

Fogging

Findings

Interval near normalization of hypo densities in the right posterior cerebral artery distribution and right thalamus in the area of previously noted infarction. This is likely represents fogging secondary to luxury perfusion. Areas of increased density may represent laminar necrosis and petechial hemorrhage.


Diagnosis: Fogging


Following infarction, there may be normalization of previous hypo density secondary to luxury perfusion. This typically occurs 2-4 weeks following the acute event. If given contrast, the area will intensely enhance homogeneously. The fogging effect occurs during the resorption stage when macrophages phagocytize necrotic material. There is loss of edema and associated mass effect. As the phagocytized material is altered and the macrophages later exit, the infarcted area becomes increasingly hypodense and finally cystic. The fogging effect is to be distinguished from the normalization of density in a low density infarct secondary to the administration of intravenous contrast.

Methylamalonic acidemia

Findings

There are oblong areas of hypointense T1, hyperintense T2 signal in the bilateral globus pallidus (Figure 1 and Figure 2). Figure 3 is a FLAIR image which does not demonstrate edema in this region. Figure 4 is a diffusion weighted image which does not show restricted diffusion, essentially excluding acute infarction.


Diagnosis: Methylamalonic acidemia


Inborn disorders of amino acid metabolism may commonly present with vomiting, feeding difficulties, lethargy, dehydration and metabolic acidosis. Neurologic symptoms include seizures, hypotonia, spasticity, developmental delay, mental retardation, and movement disorders often prompting evaluation with MR imaging.

Briefly, isoleucine, valine, methionine, and threonine are normally converted to propionic acid, methylmalonic acid, and succinic acid, the last step of which requires methylmalonyl CoA mutase and a coenzyme, adenosyl cobalamine. A deficiency in either the enzyme or coenzyme, in an autosomal recessive manner, results in the accumulation of methylmalonic acid. This build up results in the inhibition of succinate dehydrogenase; this enzyme facilitates mitochondrial aerobic glucose oxidation. The globus pallidus is particularly sensitive to mitochondrial dysfunction.

Deficiency in methylmalonyl CoA mutase generally produces earlier onset of symptoms and a more severe course with a mean survival time of 1.5 to 6.4 years.

Neuroimaging in these patients ranges from normal, with a subtle MR spectroscopy finding of elevated CSF lactate, to chronic infarction in the globus pallidus. In general, prominence of the ventricles and sulci with delayed white matter myelination may be seen. In our case, the patient was found to have chronic infarctions of the bilateral globus pallidus without additional parenchymal findings. In cases of suspected methylmalonic academia, correlation with genetic studies may be confirmatory.