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also studied by Denny-Brown.2 The Hicks kindred2V6had progressive SN and SNHL but did not appear to have a dementing illness, although "possible subnormal memory and intelligence" was reported in one caseq2The current kindred did not show the lancinating pains that were a prominent symptom in the Hicks kindred2s6and in the patient studied by Hageman et al.5 The current kindred did not have the prominent cerebellar features that occurred in the Portuguese kindred of Yee et a13; these subjects had a combination of HSAN and cerebello-olivary degeneration. The current kindred lacked autonomic symptoms a n d h a d normal results on detailed autonomic function testing. The kindred reported here is of interest because (1) hereditary SN, SNHL, and a dementing process are linked in an autosomal dominantly inherited disorder, and (2) the variability of expression, from previously reported kindreds, suggests clinical (possibly genetic) heterogeneity among kindreds with type I hereditary SN. From the Peripheral Neuropathy Research Center, Department of Neurology, Mayo Clinic and Mayo Foundation, Rochester, MN. Supported in part by grants obtained from the National Institute of Neurological Disorders and Stroke (NINDS 14304) and from the Muscular Dystrophy Association (MDA). Received August 3, 1994. Accepted in final form September 6, 1994. In vivo proton magnetic resonance spectroscopy in a case of intracranial hydatid cyst Address correspondence and reprint requests to Dr. Peter James Dyck, Peripheral Neuropathy Center, Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. References 1. Dyck PJ. Inherited neuronal degeneration and atrophy affecting peripheral motor, sensory, and autonomic neurons. In: Dyck PJ, Thomas PK, Lambert EH, eds. Peripheral neuropathy. Philadelphia: WB Saunders, 19752325-867. 2. Denny-Brown D. Hereditary sensory radicular neuropathy. J Neurol Neurosurg Psychiatry 1951;14:237-252. 3. Yee MHC, Layzer RB, Ellis WG. Hereditary sensory neuropathy with deafness and dementia: a new syndrome [abstract]. Neurology 1986;36(suppl 1):115. 4. Horoupian DS. Hereditary sensory neuropathy with deafness: a familial multisystem atrophy. Neurology 1989;39: 244-248. 5. Hageman G, Hilhorst BGJ, Rozeboom AR. Is there involvement of the central nervous system in hereditary sensory radicular neuropathy? Clin Neurol Neurosurg 1992;94:49-54. 6. Hicks EP. Hereditary perforating ulcer of the foot. Lancet 1922;1:319-321. 7. Kokmen E, Smith GE, Petersen RC, Tangalos E, Ivnik RC. The short test of mental status. Correlations with standardized psychometric testing. Arch Neurol 1991;48:725-728. 8. Dyck PJ, Kames JL, OBrien PC, Zimmerman IR. Detection thresholds of cutaneous sensation in humans. In: Dyck PJ, Thomas PK, Griffin J , Low PA, Poduslo JF, eds. Peripheral neuropathy. 3rd ed. Philadelphia: WB Saunders, 1993:706-728. 9. Low PA. Autonomic nervous system function. J Clin Neurophysiol 1993;lO:14-27. Article abstract-We performed in vivo proton magnetic resonance spectroscopy (MRS) in a patient who had an intracranial hydatid cyst. Besides lactate, alanine, and acetate, a large resonance for pyruvate was observed. These findings were further confirmed by ex vivo high-resolution NMR spectroscopy of the evacuated cyst fluid, as well as of the fluid aspirated from a cyst in the liver of the same patient. The MRS pattern appeared different from that seen in other cystic lesions of the CNS. In vivo MRS may be used as an adjunct to imaging in the diagnosis of intracranial hydatid cysts. It may also have a role in monitoring drug therapy. NEUROLOGY 1995;45:562-564 A. Kohli, MD; R.K. Gupta, MD; H. Poptani, MSc; and R. Roy, PhD The differential diagnosis of intracranial cystic lesions ranges from abscesses, neoplasms, and parasites to congenital cysts. Though there are suggestive features on imaging for each one of these, the diagnosis may sometimes remain uncertain.' Since the biochemical content of each lesion is likely to be different, particularly with respect to amino acids and respiratory cycle metabolites, an in vivo estimation may help to differentiate these cystic lesions. I t was with this objective that we performed in vivo proton magnetic resonance spectroscopy (MRS) in a patient with intracranial hydatid cyst. To the best of our knowledge, this is the first report of in vivo proton MRS of a hydatid cyst in a human host. Case report. The patient was a 12-year-old boy who 562 NEUROLOGY 45 March 1995 presented with a 3-month history of headache. In the last 2 weeks preceding admission, the headache had become severe and a mild right-sided weakness had developed. Neurologic examination showed bilateral early papilledema and a right-sided grade 4 power with hyperreflexia and extensor plantar response. There were no meningeal signs, visual field deficits, parietal lobe signs, or any other neurologic deficits. Hematologic and biochemical investigations were normal. Cranial CT showed a large cystic cavity in the left parieto-occipital area. A chest radiograph a n d a n ultrasound examination of t h e abdomen further showed a cyst in the upper lobe of the leR lung and also in the right lobe of the liver. A clinical diagnosis of multiple hydatid cysts was made. MRI and spectroscopy were performed on a 2-tesla superconducting system operating a t 1.5 tesla using a circularly polarized head coil. T,-weighted (TRPTE = 600/15) and T2-weighted (2200/80) axial and T,-weighted 3D sagittal imaging was performed using a section thick- A SE 135 STEAM 20 Figure 1. TI-weightedleft parasagittal image shows a large cyst in the parieto-occipital region causing mass effect. ness of 5 mm and inter-section gap of 0.5 mm for axial imaging, a 3-mm section thickness with no inter-section gap for sagittal images, and a 256 X 256 matrix for both types. It revealed a large single cyst occupying almost t h e whole of t h e left cerebral hemisphere; the cyst appeared hypointense on TI- and hyperintense on T2weighted images and appeared to be pushing the ventricular system to the right side (figure 1). Solvent-suppressed in vivo proton MRS was performed using s t i m u l a t e d echo acquisition mode (STEAM)2and spin-echo (SE) sequences. An 8-ml volume was chosen from the center of the cyst. Solvent suppression was achieved by the application of three consecutive chemical-shift-selective pulses (60 Hz bandwidth) centered on the water resonance. Voxel homogeneity was achieved by shimming on t h e water resonance. The width a t half-maximum of t h e water resonance was between 4 and 5 Hz after voxel shimming. After the amplitudes of the saturation pulses were adjusted for maximum solvent suppression, the spectra were obtained from the voxel with STEAM by using TE = 20/270 msec, TM = 29.5 msec, TR = 3,000msec, and 128 averages per spectrum. SE sequence with TE = 135 msec, TR = 3,000 msec, and 256 averages was done to show the phase reversal of lactate and alanine. Postprocessing of the free induction decay was done by zero filling and gaussian multiplication. Time domain spectra were analyzed by Fourier transform and were phase-corrected. The real part of the spectrum was extracted, and no baseline correction was done. STEAM 20-msec spectrum showed resonances at 1.3 ppm (assigned to lactate), 1.48 ppm (alanine), 1.92 ppm (acetate), and 2.41 ppm (pyruvate ) (figure 2A). On SE 135 msec, resonance at 1.3 ppm and 1.48 ppm showed inversion, confirming the lactate and alanine (figure 2A). The J coupling constant for methyl resonance of lactate was 7 Hz. The complete cyst with intact membrane could be removed on surgery, and the diagnosis was confirmed on histologic study as Echinococcus granulosus. Fluid was collected from the evacuated cyst and from the liver cyst, and ex vivo high-resolution NMR was performed using a B +.a 3.5 1.1 2.5 2.1 1,s I.? .s I1 . . I Figure 2. (A) STEAM 20-msec spectrum shows resonances at 2.41 ppm (assigned to pyruvate), 1.92 ppm (acetate), 1.48 ppm (alanine), and 1.3 pprn (lactate). At SE 135 msec, alanine and lactate show inversion. (B) Single-pulse ex vivo spectrum confirms the above assignments. (LAC = lactate, AL = alanine, AC = acetate, P = pyruvate, TSP = sodium 3-trimethyl propionate.) 400-MHz spectrometer (Brukers, Switzerland). In each case 450 pl of fluid was taken in a 5-mm NMR tube and 10% D20(7.5%sodium 3-trimethyl propionate [TSP]) was added to make 500 p1. A single-pulse spectrum was obtained with a repetition time of 60 msec, a pulse angle of 65", and 256 acquisitions. The presaturation pulse was used for water suppression. It confirmed the assignments seen in vivo, ie, lactate (1.3 pprn), alanine (1.48 ppm), acetate (1.92 ppm), and pyruvate (2.41 ppm) (figure 2B). The in vivo spectral assignment was done by placing the methyl resonance of lactate a t 1.3 ppm, and the ex vivo spectral assignment was done by placing the external reference (TSP) a t 0.0 ppm. These assignments were based on the previously reported chemical shift^.^ The pyruvate resonance was confirmed by adding pyruvate to the sample. The spectra from the brain and liver cyst fluids were identical. March 1995 NEUROLOGY 46 683 Discussion. The hydatid cyst is a metabolically active cavity. The inner lining membrane, which is the germinal layer, is persistently generating new smaller cysts or protoscoleces. Characteristically, the hydatid cyst has an active glycolytic pathway and further relies on anaerobic pathways as well as the tricarboxylic acid cycle for energy production. In vitro studies have shown the intermediaries of all these metabolic pathways in the cyst contents but particularly higher concentrations of pyruvate, lactate, acetate, and alanine.4s5The cyst also contains a large array of amino acids, of which glycine occurs in notable amounts. Pyruvate is present as an end result of glycolysis and may be metabolized via the aerobic pathway to acetate or via the anaerobic pathway to l a ~ t a t eAlanine .~ has also been identified as an end product of pyruvate metabolism in helminths, with glutamate acting as an amino d o n ~ r . ~ ? ~ In the only other study we found where in vivo and in vitro MRS was performed in the hydatid cyst, large amounts of succinate, acetate, alanine, creatine, glycine, and lactate were shown.3 The study was performed on Echinococcus multilocularis cysts grown subcutaneously i n Meriones unguiculatus. Although there was concurrence on all other findings, we did not find succinate as reported i n t h e above study. T h i s could be explained on the basis of the known differences in metabolism between E multilocularis and E granuZosus, which causes the commonly seen hydatid cysts in the human host.4 In vivo MRS is now extensively used in the characterization of intracranial space-occupying lesions a s well as in the study of metabolically altered brain tissue such as infarction and epileptogenic tissue.6 Altered tissue turnover components as well as metabolites are the basis of tissue characterization.6 The combination of pyruvate, alanine, and acetate was the distinctive feature of the in vivo MRS study of the hydatid cyst. This finding also coincides with ex vivo studies of the fluid from the same cyst as well as fluid aspirated from another cyst in the liver. In our experience of in vivo MRS in more than 32 biopsy-confirmed intracranial cysts of almost all other types, we did not record the same distinctive combination (unpublished data). The present approach to t h e t r e a t m e n t of 664 NEUROLOGY 45 March 1B96 hydatid cysts aims at a sterile cyst fluid prior to surgery. This is due to the hazards of spillage of viable protoscoleces, with resulting toxicity and recurrence. Albendazole, which is presently the most effective drug, makes the protoscoleces inviable and causes structural changes in the inner membrane.' An understanding of the metabolite information available by in vivo MRS may make it possible to differentiate live, degenerating, and dead cysts and may also help in evaluating the effect of chemotherapy. Although t h e i n vivo a n d ex vivo r e s u l t s appeared consistent, a single report is not sufficient to characterize t h e MRS features of t h e hydatid cyst. Further studies in a large number of patients may be required to substantiate the above findings. The diagnostic and therapeutic implications appear promising. From the Department of Neurology (Dr. Kohli) and the MR Section, Department of Radiology (Dr. Gupta and H. Poptani), Sanjay Gandhi Post Graduate Institute of Medical Sciences, and the Central Drug Research Institute (Dr. Roy), Lucknow, India. Received June 1, 1994.Accepted in final form September 7, 1994. Address correspondence and reprint requests to Dr. Anoop Kohli, Department of Neurology, SGPGIMS, PB 375,Lucknow 226014,India. References 1. Sartor K. MR imaging of the skull and brain: a correlative text atlas. Heidelberg, Germany: Springer-Verlag, 1992:630. 2. Frahm J, Merboldt KD, Hanicke W. Localized proton spectroscopy using stimulated echoes. J Magn Reson Imaging 1987;72:502-508. 3. Novak M, Hameed N, Buist R, Blackburn BJ. Metabolites of alveolar Echinococcus as determined by 31-P and 1-H nuclear magnetic resonance spectroscopy. Parasitol Res 1992;78: 665-670. 4. McManus DP, S m y t h J D . Intermediary carbohydrate metabolism in protoscoleces of Echinococcus granulosus (horse and sheep strains) and E. multilocularis. Parasitology 1982;84:351-366. 5. Hurd H. Echinococcus granulosus: a comparison of free amino acid concentration in hydatid fluid from primary and secondary cysts and host plasma. Parasitology 1989;98:135143. 6. Howe FA, Maxwell RJ, Saunders DE, Brown MM, Griffiths JR.Proton spectroscopy in vivo. Magn Reson Q 1993;9:31-59. 7. Gil-Grande LA, Caabeiro FR, Prieto JG, et al. Randomised controlled trial of efficacy of albendazole in intra-abdominal hydatid disease. Lancet 1993;342:1269-1272.