¹Departments of Oncology and Pediatrics, Johns Hopkins Hospital, Baltimore, MD, USA

²Russell H Morgan Department of Radiology, Johns Hopkins Hospital, Baltimore, MD, USA

Correspondence to: Dr A R Chen, Department of Pediatric Oncology, CMSC 800, Johns Hopkins Hospital, 600 N, Wolfe St, Baltimore, MD 21287, USA

We report a case of posterior reversible leuko- encephalopathy (PRL) following the infusion of dimethylsulfoxide (DMSO) cryopreserved autologous stem cells in the setting of myeloablative chemotherapy in a patient with recurrent Ewing's sarcoma. Magnetic resonance (MR) imaging revealed white matter changes which resolved over the next 2 months. Bone Marrow Transplantation (2000) 26, 797-800.

DMSO; leukoencephalopathy; MRI; stem cell infusion; reversible

Reversible posterior leukoencephalopathy syndrome (RPL) is characterized by white matter edema predominantly in the posterior parietal, temporal and occipital regions of the brain with characteristic clinical symptoms of headache, altered mental status, seizures and visual changes.¹ This clinical and radiographic syndrome has been reported in association with hypertensive encephalopathy, eclampsia, renal failure with hypertension and immunosuppression most notably with cyclosporine and tacrolimus.^1,2,3,4,5 RPL has not previously been recognized in association with DMSO infusion. Reversible central neurotoxicity has been described in two patients with high levels of DMSO after infusion of cryopreserved autologous peripheral blood stem cells, without neuroimaging.⁶ We report a case of reversible leukoencephalopathy associated with infusion of DMSO-cryopreserved stem cells in which the initial leukoencephalopathy and resolution are demonstrated radiographically.

Case report

RD is a 16-year-old Caucasian female diagnosed as having non-metastatic Ewing's sarcoma of the chest wall in May 1996. She was treated on the intergroup Ewing's sarcoma study (POG 9354/CCG6742 regimen A) with vincristine, doxorubicin, cyclophosphamide, ifosfamide, and etoposide over 30 weeks and local control by surgical resection at 12 weeks. Sixteen months after the completion of her therapy, she developed a cough associated with a large pleural effusion and a 7.5 ´ 9-cm posterior mediastinal mass arising from the right chest wall, pathologically confirmed to be recurrent Ewing's sarcoma.

She was referred for myeloablative chemotherapy with stem cell rescue. In August 1998, she received cyclophosphamide (4 g/m² i.v.) followed by 10 g/kg/day G-CSF to mobilize stem cells which were collected by leukapheresis. CD34⁺ cells were isolated using the Isolex 300i (Baxter, Deerfield, IL, USA) and preserved in 10% DMSO/17.5% Plasmalyte A/22.5% autologous irradiated plasma and stored in liquid nitrogen. Salvage chemotherapy included ifosfamide, carboplatin and etoposide with a good initial response, but the tumor progressed locally and was not operable. She received docetaxel, which produced a good partial response, and underwent a gross total resection of the residual tumor.

Her pre-transplant evaluations were satisfactory with the exception of a residual pleural effusion and spirometry that showed moderate restrictive lung disease, marginal renal function with a baseline creatinine clearance of 70 ml/min/1.73 m², and peripheral neuropathy attributed to vincristine and docetaxel.

RD received carboplatin (725 mg/m²/day ´ 3 days) with etoposide (800 mg/m²/day continuous infusion ´ 3 days) followed by cyclophosphamide (60 mg/kg/day ´ 2 days) with MESNA. RD became drowsy but remained oriented and she noted a mild esophoria following her chemotherapy on day -1 before stem cell infusion. This was attributed to her ondansetron anti-emetic therapy and possibly, carboplatin toxicity. Her medications were reviewed and included diphenhydramine hydrochloride which was changed to loratadine, dexamethasone, ranitidine, furosemide, hydromorphone hydrochloride as needed, piperacillin/ tazobactam, amikacin and fluconazole. A CT scan of the head showed only mild cerebral atrophy. A lumbar puncture was attempted without success. Laboratory studies demonstrated the onset of renal insufficiency as indicated by a marked acidosis and serum creatinine rising from 0.5 mg/dl to 1.8 mg/dl. She was medically managed with intravenous fluids. Her estimated creatinine clearance on the day of stem cell infusion was 19 ml/min/1.73 m². She was infused with 2.32 ´ 10⁶ CD34⁺ cells/kg suspended in 20 ml medium with 10% DMSO over 15 min on day 0. Two hours after infusion of her cells, she became hypothermic (34.8°C), somnolent and disoriented to place and time. Medication that could cause sedation was decreased and antibiotic coverage was broadened. A venous blood gas revealed a pH of 7.15 and a calculated bicarbonate of 8 mmol/l which was corrected slowly over the following 24 h. Her electrolytes remained stable. On day +1, she developed bradycardia to 43 beats per min and an echocardiogram demonstrated moderate decrease in left ventricular function. She was transferred to the intensive care unit and begun on an isoproterenol drip for chronotropic support. Her blood pressure remained stable during this time with only a transient increase when the isoproterenol was initiated. An MR of the brain on day +1 revealed mild atrophy and multifocal subcortical white matter signal abnormalities (high T2, low T1 signal) initially thought to be consistent with the effects of prior chemotherapy.

On day +2, RD had a seizure with head deviation to the right followed by generalized tonic clonic movement lasting less than 1 min. She was treated with fosphenytoin. A non-contrast CT revealed a 5 ´ 3-cm low attenuation lesion in the left fronto-temporal region. An MR that day demonstrated extensive subcortical white matter changes (Figure 1). Septic embolism was suspected, but not substantiated by evaluations including MRA of the brain, echocardiography, ophthalmologic examination, general physical examination and negative blood cultures. Because of the low yield of cerebral spinal fluid culture in this setting and the condition of the patient, antibiotic coverage was empirically increased to include vancomycin and Amphotec (Sequus Pharmaceuticals, Menlo Park, CA, USA). She had one additional tonic-clonic seizure on day +3 which resolved without further intervention. Her sensorium normalized over the next 5 days, despite worsening renal failure with BUN peaking at 115 mg/dl on day +11 and creatinine 6.1 mg/dl on day +10. She was weaned off fosphenytoin and has had no further seizure activity. Two months after stem cell infusion, MR examination demonstrated almost complete resolution of the white matter and physical examination showed no central neurologic deficit.

Discussion

Dimethyl sulfoxide (DMSO) is a water-miscible clear liquid employed in the cryopreservation of stem cells used in autologous bone marrow infusion. DMSO is oxidized to dimethylsulphdioxide (DMSO₂) by liver microsomes in the presence of molecular oxygen and NADPH₂. DMSO₂ and to a lesser extent dimethylsulphide (DMS), another metabolite, are detected in the plasma within 5 min of intravenous infusion and are excreted via the kidney. Three to 6% of DMSO is excreted by the lungs as DMS, giving the characteristic odor associated with the infusion.^7,8,9 DMSO is FDA approved for treatment of interstitial cystitis,¹⁰ but is universally used as a cryopreservant and has also been used for various indications including arthritis, skin disorders and post-herpetic neuralgia.^8,11 Toxicology studies in humans and animals report numerous side-effects dependent on dose and route of administration.^7,12 Most commonly, nausea and vomiting are associated with the infusion of cryopreserved stem cells. In addition hypotension or hypertension, chest tightness, respiratory distress, bradycardia and muscle cramps have been reported. Less commonly reported toxicities include intravascular hemolysis, hypothermia, liver damage and central nervous system effects including sedation and seizures.^12,13,14

Following myeloablative chemotherapy, RD began to develop acute renal insufficiency as evidenced by rising serum creatinine and metabolic acidosis. At the time of her stem cell infusion, her BUN was 24 and creatinine was 1.8 mg/dl. She developed bradycardia and hypothermia, known toxicities of DMSO, following the infusion of her cryopreserved stem cells. She became somnolent and subsequently had a tonic-clonic seizure. DMSO levels were not obtained, but because of her deteriorating renal function, her excretion of DMSO and its metabolites would be expected to be prolonged. MR images revealed the presence of multiple foci of subcortical abnormalities. No infectious etiology could be identified and a thromboembolic source was ruled out via flow void analysis. RD had an elevated AST which peaked at 1371 IU/l on day 0 and rapidly normalized, as is typical of this preparative regimen. Her ammonia was within normal limits.

MRI is highly sensitive in detecting pathological processes involving the brain. Anatomical distribution can be beneficial in determining the underlying etiology. FLAIR (fluid attenuated inversion recovery) is an MR sequence used to suppress signals from CSF. Small lesions near the ventricles are better visualized with FLAIR techniques than with T2-weighted techniques. High T2 and FLAIR signal in the gray matter is typically attributable to cytotoxic edema. A vascular distribution is suggestive of infarction. A non-vascular distribution can be seen with infectious encephalitides or with the reversible posterior leukoencephalopathies.¹⁵ The latter are felt to be due to changes in autoregulation. This syndrome has been associated with hypertensive processes (malignant hypertension, eclampsia, cyclosporine toxicity) or uremic encephalopathies (uremia/glomerulonephritis, hemolytic-uremic syndrome and thrombotic thrombocytopenic purpura).¹⁵ These entities usually present with bilaterally symmetric confluent lesions centered in the immediate subcortical white matter of the occipital lobes, although they may also occur in the posterior fossa (cerebellum and pons), as well as the frontal lobes and the corpus callosum. Contrast enhancement can be seen, and if present tends to be somewhat patchy. Classically, the MR abnormalities as well as the neurological deficits resolve completely within several weeks after blood pressure control or normal blood urea nitrogen levels are attained, with no residual morphological changes observed.

Two cases of somnolence and decreased responsiveness have been reported following DMSO-cryopreserved stem cell infusion in patients with renal insufficiency.⁶ The plasma DMSO level was measured in the first case because of a persistent garlic odor and was found to be elevated 6 days after stem cell infusion. Plasmapheresis resulted in an abrupt decline in the DMSO level and rapid improvement in the patient's mental status. As in the previously reported cases, RD had renal insufficiency at the time of stem cell infusion. We attribute her reversible posterior leukoencephalopathy to DMSO rather than to renal insufficiency because she was not uremic when she developed the leukoencephalopathy, and even as she became frankly uremic over the next 10 days her mental status improved. We believe the role of renal insufficiency in this case was to increase the exposure to DMSO. RD had only a transient increase in blood pressure following the initiation of isoproterenol and so hypertensive encephalopathy was not the etiology of her seizure. She had never received CsA or tacrolimus.

In this report, we demonstrate reversible areas of T2 signal hyperintensity involving the gray matter. These areas do not conform to a vascular distribution and there were no clinical findings to suggest infectious encephalitis. Although the asymmetric distribution is somewhat atypical for a reversible posterior leukoencephalopathy, the bilateral involvement and reversibility suggest that this process may be considered a reversible posterior leukoencephalopathy. A toxicity mechanism similar to cyclosporine and tacrolimus in the autoregulatory mechanism may underlie this process. Further investigation will be needed to better delineate the similarities between DMSO toxicity and the reversible posterior leukoencephalopathy. The neurologic toxicity of DMSO is likely to be more common than reported as the symptoms may not be as dramatic as those seen in our patient and may be explained by other medications that the patient is receiving. DMSO toxicity should be suspected in patients with decreased renal function at the time of stem cell infusion. Patients who receive unselected stem cells may receive five to 15-fold more DMSO and are therefore at greater risk. If profound neurologic morbidity is seen, plasmapheresis may improve the patient's clinical status. Alternatively, to protect patients who have renal insufficiency before stem cell infusion, it is possible to reduce DMSO exposure by washing the cells prior to re-infusion. However this procedure may result in cell loss and cell clumping. While posterior leukoencephalopathy is generally thought to be reversible once the cause is identified and eliminated, case reports have described irreversible neurological damage^16,17 and so prompt identification and elimination of the underlying cause is required.

Acknowledgements

We thank Dr Georgia Vogelsang for her comments on the paper.

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Figure 1 FLAIR MR images (TR, 9002; TI, 2200; TE, 133 ms) demonstrate signal hyperintensity focally involving the gray matter near the right calcarine fissure (a, arrowhead). There were also gyriform areas of increased T2-weighted signal involving the cortex of the left frontal lobe (b, arrowhead) and left medial occipital lobe (b, arrow), with probable subcortical white matter involvement in the left occipital lobe region. The next day, FLAIR MR images (TR, 8802; TI, 2200; TE, 124 ms) at the same level show dramatic progression in the size and extent of the signal abnormality, with extensive involvement of both cortex and subcortical white matter; predominately in a gyriform pattern. New lesions are also present in the left frontal (c, d arrowheads) and occipital lobes (c, arrow) as well as the right parietal lobe (d, arrow). Following the administration of gadolinium, T1-weighted images (TR, 500; TE, 20) show gyriform enhancement of the meninges in the same distribution as the T2 abnormalities (e, f). Two months after the initial examination, the MR scan was normal, with complete resolution of the pathologic process (not shown).