- Email: [email protected]
Hydatid cysts of the internal acoustic canal and jugular foramen
394
Case reports / Journal of Clinical Neuroscience 14 (2007) 394–396
8. Tarantino R, Esposito V, Missori P, et al. Occipitocervical pseudomalignant osseous tumor of the soft tissue (Fasciitis ossificans). Case report. J Neurosurg 2001;95:143–5. 9. Kwittken J, Branche M. Fasciitis ossificans. Am J Clin Pathol 1969;51:251–5. 10. Uhe S, Evert M, von Falkenhausen U, et al. Fasciitis ossificans of the paranasal sinus. Ann Otol Rhinol Laryngol 2004;113:558–61. 11. Ackerman LV. Extra-osseous localized non-neoplastic bone and cartilage formation (so-called myositis ossificans): clinical and pathological confusion with malignant neoplasms. J Bone Joint Surg (Am) 1958;40:279–98. 12. Nieto del Rincon N, Guibelalde del Castillo M, Herrera Savall M, et al. [What is your diagnosis? Infraclavicular mass. Myositis ossificans non traumatic]. An Pediatr (Barc) 2004;61:197–8, In Spanish. 13. Risto O, Wahlstrom O, Abdiu A. The effect of low dose diclofenac sodium administered locally on heterotopic bone formation in rats. Int Orthop 1995;19:392–5.
14. Nilsson OS, Bauer HC, Brosjo O, et al. A comparison of indomethacin and diclofenac in the inhibition of experimental heterotopic new bone formation. Int Orthop 1987;11:283–7. 15. Larson CM, Almekinders LC, Karas SG, et al. Evaluating and managing muscle contusions and myositis ossificans. Phys Sportsmed 2002;30:22–9. 16. Harmon DC, Petur Nielsen G. Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 38-1994. A 55-year-old man with a paraspinal mass and a history of radiation treatment of a testicular tumor. N Engl J Med 1994;331:1079–84. 17. Hartmann R, Bottger E. [Unusual course of localised myositis ossificans with radiation therapy]. Fortschr Geb Rontgenstr Nuklearmed 1973;119:116–9, In German. 18. Heermeier K, Spanner M, Trager J, et al. Effects of extremely low frequency electromagnetic field (EMF) on collagen type I mRNA expression and extracellular matrix synthesis of human osteoblastic cells. Bioelectromagnetics 1998;19:222–31.
doi:10.1016/j.jocn.2006.01.009
Hydatid cysts of the internal acoustic canal and jugular foramen Go¨khan Akdemir a
a,*
, Ergu¨n Dag˘lıog˘lu b, Mehmet Sec¸er b, Mehmet Fikret Ergu¨ngo¨r
b
Mustafa Kemal University, Tayfur Ata So¨kmen Medical School, Department of Neurosurgery, 3100 Hatay, Turkey b Ankara Numune Training and Research Hospital, Department of Neurosurgery, Ankara, Turkey Received 25 December 2005; accepted 22 April 2006
Abstract Brain involvement with hydatid disease occurs in 1–2% of all Echinococcus granulosus infections. Cerebral hydatid cysts are usually supratentorial, whereas infratentorial lesions are quite rare. Here we report a 19-year-old man with hydatid cysts in the right cerebellopontine cistern with the involvement of internal acoustic canal and jugular foramen. The patient presented with signs of increased intracranial pressure and multiple cranial nerve palsies. Surgery was performed in the semi-sitting position using a lateral suboccipital approach for a right-sided craniotomy. Magnetic resonance imaging clearly demonstrated cisternal, neural and vascular relationships which aided in intact surgical removal of the lesion using microsurgical techniques. Total removal without rupture should be the surgical goal in all hydatid cysts. 2006 Elsevier Ltd. All rights reserved. Keywords: Cerebellopontine cistern; Cerebral hydatid cyst; Internal acoustic canal; Jugular foramen; Magnetic resonance imaging
1. Introduction Hydatid disease is an endemic parasitic infection encountered especially in areas where people live in close contact with dogs and sheep.1 It is caused by the dog tapeworm Echinococcus granulosus and can involve any part of the body. Two predominant sites for hydatid cysts are the liver and the lungs, whereas the central nervous system is involved in 2–3% of the cases.2,3 More than 90% of cystic echinococcosis lesions are supratentorial. The infratentorial region is an unusual location for hydatid cysts.1 Cysts *
Corresponding author. Tel.: +90 326 214 8661; fax: +90 326 241 5702. E-mail address: [email protected] (G. Akdemir).
typically occur within the brain parenchyma and are often solitary. Infratentorial cisterns or intraventricular regions are unusual sites of involvement. Here we report a case of right cerebellopontine cistern hydatid cysts with a special emphasis on magnetic resonance imaging (MRI) and the surgical procedure. 2. Case report A 19-year-old man was admitted with intense headache, nausea, vomiting and progressive disturbance of gait over the previous 2 months. Neurological examination revealed bilateral papilledema, right-sided 5th, 7–11th nerve palsies and right cerebellar signs. His past history revealed hydatid
Case reports / Journal of Clinical Neuroscience 14 (2007) 394–396
395
disease of the liver which was surgically removed 2 years previously. Cranial computerized tomography (CT) scan was normal at the time of liver involvement. Cranial MRI was performed this time and a cystic lesion 43 · 40 · 45 mm, involving the right internal acoustic canal and jugular foramen was detected in the cerebellopontine cistern (Figs. 1 and 2). Spinal MRI did not reveal any lesions. Surgery was performed in the semi-sitting position with a lateral suboccipital approach for a right-sided craniotomy. Multiple cysts, firmly attached to cranial nerves and arachnoid membranes, were noticed in the lateral cerebellopontine cisterns. All cysts were carefully dissected and removed from cranial nerves, arachnoid membranes, internal acoustic canal and jugular foramen. Histopathological examination confirmed the cysts to be hydatid. Postoperative course was uneventful and the patient was discharged 5 days after the operation. Cranial nerve abnormalities improved markedly 3 months after the operation and a CT scan did not show recurrence. 3. Discussion
Fig. 1. T2-weighted axial MRI showing a large hyperintense lesion with no peripheral edema. Note significant mass effect on the brainstem and 4th ventricle. Arrows indicate the extension of the lesion into the internal acoustic meatus.
Fig. 2. T2-weighted axial MRI showing a large hyperintense lesion with no peripheral edema. Note significant mass effect on the brainstem and 4th ventricle. Arrows indicate the extension of the lesion into the jugular foramen.
Cerebral hydatid cysts are usually acquired in childhood and grow slowly. These lesions are often supratentorial and located in the watershed zones of the middle cerebral arterial territory.2 They present with symptoms of headache and vomiting due to increased intracranial pressure.1 Hemiparesis, papilledema, and seizure are other common signs. Infratentorial localization of these cysts is rare.1,4,5 However, symptoms of obstructive hydrocephalus due to the 4th ventricular or aqueductal compression, as well as dysmetria, nystagmus, cranial nerve findings and truncal ataxia due to vermis and cerebellum involvement are commonly encountered. More than 50 patients are reported with hydatid cysts in the posterior fossa, including the cerebellum, posterior cerebral artery angle, 4th ventricle and the aqueduct of Sylvius.5–8 However, there are only two reported cases of intracisternal cysts, namely in the premedullary9 and basal cisterns.3 The hydatid cysts reported here were localized in the right cerebellopontine cistern and we confirmed their intracisternal location during the operation. In the cerebral cisterns, the most likely pathway of dissemination is haematogenous spread to the meninges and rupture of a primary cyst into the subarachnoid space.3 Magnetic resonance imaging is the best choice to diagnose a hydatid cyst. On MRI, the signal from the cyst is nonhomogeneous: iso- or hypointense on T1-weighted and hyperintense on T2-weighted images. Compared to CT scan, MRI is more reliable for detecting the irregularities at the rim border. In addition, MRI can estimate the thickness of the rim. The pericyst shows contrast enhancement. The sensitivity of MRI together with its multiplanar imaging capabilities, allows for accurate detection, localization and assessment of affected structures and for infratentorial hydatid lesions, the relationship with cranial nerves and vascular architecture are visualized more precisely.1,2,9–11
396
Case reports / Journal of Clinical Neuroscience 14 (2007) 396–398
Regarding the differential diagnosis of hydatid cysts, arachnoid cysts and epidermoids are common in the cerebellopontine cisterns.7 Cystic astrocytomas, porencephalic cysts and pyogenic or fungal abscesses are other lesions to be differentiated.2 Epidermoid cysts, being the third most common cerebellopontine angle tumor, usually have slightly hyperintense signal intensity on proton density MRI. These lesions usually surround neighboring nerves and vessels, whereas arachnoid and hydatid cysts displace adjacent structures.8 The differential diagnosis of meningioma, hemangioma, glomus tumor, cystic astrocytomas and abscesses may be confirmed by the absence of a mural nodule, perifocal edema and contrast enhancement. Arachnoid cysts and porencephalic cysts do not show contrast enhancement as much as hydatid cysts. On the other hand, diffusion MRI is not very useful because both hydatid and arachnoid cysts show increased diffusion.1,2 The treatment of choice for supratentorial cerebral hydatid cyst is cautious surgical removal without rupture. This is more difficult when the hydatid cyst is located in the cerebellopontine cisterns, as the cranial nerves and vascular structures in this region are tightly adhered to the hydatid cyst membrane and if cyst is removed without microdissection, it may result in neural and vascular harm as well as unexpected rupture. In conclusion, MRI is a valuable diagnostic technique to visualize cisternal hydatid cysts and to differentiate them from other cystic lesions and tumors. MRI can precisely define the relationship of the cyst with the vascular and neural
structures, as well as the jugular foramen and the internal acoustic canal which is important in pre-operative planning. References 1. Abbassion K, Amirjamshidi A. Diagnosis and management of hydatid cyst of the central nervous system: Part 1: General considerations and hydatid disease of the brain. Neurosurg Q 2001;11:1–9. 2. Ersahin Y, Mutluer S, Gu¨zelbag E. Intracranial hydatid cyst in children. Neurosurgery 1993;33:219–25. 3. Tistouridis J, Dimitriadis AS, Kazana E. MR in cisternal hydatid cysts. AJNR Am J Neuroradiol 1997;18:1586–7. 4. Altıno¨rs N, Bavbek M, Caner HC, et al. Central nervous system hydatidosis in Turkey: a cooperative study and literature survey analysis of 458 cases. J Neurosurg 2000;93:1–8. 5. Villarejo F, Blazquez MG, Arcas J, et al. Hydatid cyst of the posterior fossa: case report. Neurosurgery 1983;12:228–9. 6. Akdemir G, Ergu¨n R, Gezici AR, et al. Multiple hydatid cyst of aqueduct of Sylvius. Case report with MR Imaging study. Turk Neurosurg 2000;10:142–4. 7. Mascalchi M. Pontine hydatid cyst in association with an acoustic neurinoma. MR appearance in an unusual case. AJNR Am J Neuroradiol 1991;12:190–3. 8. Vaquero J, Jimenez C, Martinez R. Growth of hydatid cysts evaluated by CT scanning after presumed cerebral hydatid embolism. J Neurosurg 1982;75:837–8. 9. Rumboldt Z, Jednacak H, Talan-Hranilovic J, et al. Unusual appearance of a cisternal hydatid cyst. AJNR Am J Neuroradiol 2003;24: 112–4. 10. Von Sinner WN, Strake TEL, Clark D, et al. MR imaging in hydatid disease. AJR Am J Roentgenol 1991;157:741–5. 11. Tien RD, Macfall J, Heinz ER. Evaluation of complex cystic masses of the brain: value of steady-state free-precession MR imaging. AJR Am J Roentgenol 1992;159:1049–55.
doi:10.1016/j.jocn.2006.04.007
Quetiapine successfully treating oculogyric crisis induced by antipsychotic drugs Philippos Gourzis a b
a,*
, Panagiotis Polychronopoulos b, Andreas A. Argyriou b, Elisabeth Chroni b, Stavroula Beratis a
Department of Psychiatry, University of Patras Medical School, Rion-Patras, Greece Department of Neurology, University of Patras Medical School, Rion-Patras, Greece Received 14 November 2005; accepted 22 April 2006
Abstract We report two patients who developed persistent oculogyric crisis, obsessional thoughts and psychiatric symptoms after prolonged treatment with typical and atypical antipsychotics. Both our patients did not improve after withdrawal of these antipsychotics, but rather after quetiapine was administered. 2006 Elsevier Ltd. All rights reserved. *
Corresponding author. Tel.: +30 2610 999 728; fax: +30 260 994 534. E-mail address: [email protected] (P. Gourzis).
Case reports / Journal of Clinical Neuroscience 14 (2007) 394–396
8. Tarantino R, Esposito V, Missori P, et al. Occipitocervical pseudomalignant osseous tumor of the soft tissue (Fasciitis ossificans). Case report. J Neurosurg 2001;95:143–5. 9. Kwittken J, Branche M. Fasciitis ossificans. Am J Clin Pathol 1969;51:251–5. 10. Uhe S, Evert M, von Falkenhausen U, et al. Fasciitis ossificans of the paranasal sinus. Ann Otol Rhinol Laryngol 2004;113:558–61. 11. Ackerman LV. Extra-osseous localized non-neoplastic bone and cartilage formation (so-called myositis ossificans): clinical and pathological confusion with malignant neoplasms. J Bone Joint Surg (Am) 1958;40:279–98. 12. Nieto del Rincon N, Guibelalde del Castillo M, Herrera Savall M, et al. [What is your diagnosis? Infraclavicular mass. Myositis ossificans non traumatic]. An Pediatr (Barc) 2004;61:197–8, In Spanish. 13. Risto O, Wahlstrom O, Abdiu A. The effect of low dose diclofenac sodium administered locally on heterotopic bone formation in rats. Int Orthop 1995;19:392–5.
14. Nilsson OS, Bauer HC, Brosjo O, et al. A comparison of indomethacin and diclofenac in the inhibition of experimental heterotopic new bone formation. Int Orthop 1987;11:283–7. 15. Larson CM, Almekinders LC, Karas SG, et al. Evaluating and managing muscle contusions and myositis ossificans. Phys Sportsmed 2002;30:22–9. 16. Harmon DC, Petur Nielsen G. Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 38-1994. A 55-year-old man with a paraspinal mass and a history of radiation treatment of a testicular tumor. N Engl J Med 1994;331:1079–84. 17. Hartmann R, Bottger E. [Unusual course of localised myositis ossificans with radiation therapy]. Fortschr Geb Rontgenstr Nuklearmed 1973;119:116–9, In German. 18. Heermeier K, Spanner M, Trager J, et al. Effects of extremely low frequency electromagnetic field (EMF) on collagen type I mRNA expression and extracellular matrix synthesis of human osteoblastic cells. Bioelectromagnetics 1998;19:222–31.
doi:10.1016/j.jocn.2006.01.009
Hydatid cysts of the internal acoustic canal and jugular foramen Go¨khan Akdemir a
a,*
, Ergu¨n Dag˘lıog˘lu b, Mehmet Sec¸er b, Mehmet Fikret Ergu¨ngo¨r
b
Mustafa Kemal University, Tayfur Ata So¨kmen Medical School, Department of Neurosurgery, 3100 Hatay, Turkey b Ankara Numune Training and Research Hospital, Department of Neurosurgery, Ankara, Turkey Received 25 December 2005; accepted 22 April 2006
Abstract Brain involvement with hydatid disease occurs in 1–2% of all Echinococcus granulosus infections. Cerebral hydatid cysts are usually supratentorial, whereas infratentorial lesions are quite rare. Here we report a 19-year-old man with hydatid cysts in the right cerebellopontine cistern with the involvement of internal acoustic canal and jugular foramen. The patient presented with signs of increased intracranial pressure and multiple cranial nerve palsies. Surgery was performed in the semi-sitting position using a lateral suboccipital approach for a right-sided craniotomy. Magnetic resonance imaging clearly demonstrated cisternal, neural and vascular relationships which aided in intact surgical removal of the lesion using microsurgical techniques. Total removal without rupture should be the surgical goal in all hydatid cysts. 2006 Elsevier Ltd. All rights reserved. Keywords: Cerebellopontine cistern; Cerebral hydatid cyst; Internal acoustic canal; Jugular foramen; Magnetic resonance imaging
1. Introduction Hydatid disease is an endemic parasitic infection encountered especially in areas where people live in close contact with dogs and sheep.1 It is caused by the dog tapeworm Echinococcus granulosus and can involve any part of the body. Two predominant sites for hydatid cysts are the liver and the lungs, whereas the central nervous system is involved in 2–3% of the cases.2,3 More than 90% of cystic echinococcosis lesions are supratentorial. The infratentorial region is an unusual location for hydatid cysts.1 Cysts *
Corresponding author. Tel.: +90 326 214 8661; fax: +90 326 241 5702. E-mail address: [email protected] (G. Akdemir).
typically occur within the brain parenchyma and are often solitary. Infratentorial cisterns or intraventricular regions are unusual sites of involvement. Here we report a case of right cerebellopontine cistern hydatid cysts with a special emphasis on magnetic resonance imaging (MRI) and the surgical procedure. 2. Case report A 19-year-old man was admitted with intense headache, nausea, vomiting and progressive disturbance of gait over the previous 2 months. Neurological examination revealed bilateral papilledema, right-sided 5th, 7–11th nerve palsies and right cerebellar signs. His past history revealed hydatid
Case reports / Journal of Clinical Neuroscience 14 (2007) 394–396
395
disease of the liver which was surgically removed 2 years previously. Cranial computerized tomography (CT) scan was normal at the time of liver involvement. Cranial MRI was performed this time and a cystic lesion 43 · 40 · 45 mm, involving the right internal acoustic canal and jugular foramen was detected in the cerebellopontine cistern (Figs. 1 and 2). Spinal MRI did not reveal any lesions. Surgery was performed in the semi-sitting position with a lateral suboccipital approach for a right-sided craniotomy. Multiple cysts, firmly attached to cranial nerves and arachnoid membranes, were noticed in the lateral cerebellopontine cisterns. All cysts were carefully dissected and removed from cranial nerves, arachnoid membranes, internal acoustic canal and jugular foramen. Histopathological examination confirmed the cysts to be hydatid. Postoperative course was uneventful and the patient was discharged 5 days after the operation. Cranial nerve abnormalities improved markedly 3 months after the operation and a CT scan did not show recurrence. 3. Discussion
Fig. 1. T2-weighted axial MRI showing a large hyperintense lesion with no peripheral edema. Note significant mass effect on the brainstem and 4th ventricle. Arrows indicate the extension of the lesion into the internal acoustic meatus.
Fig. 2. T2-weighted axial MRI showing a large hyperintense lesion with no peripheral edema. Note significant mass effect on the brainstem and 4th ventricle. Arrows indicate the extension of the lesion into the jugular foramen.
Cerebral hydatid cysts are usually acquired in childhood and grow slowly. These lesions are often supratentorial and located in the watershed zones of the middle cerebral arterial territory.2 They present with symptoms of headache and vomiting due to increased intracranial pressure.1 Hemiparesis, papilledema, and seizure are other common signs. Infratentorial localization of these cysts is rare.1,4,5 However, symptoms of obstructive hydrocephalus due to the 4th ventricular or aqueductal compression, as well as dysmetria, nystagmus, cranial nerve findings and truncal ataxia due to vermis and cerebellum involvement are commonly encountered. More than 50 patients are reported with hydatid cysts in the posterior fossa, including the cerebellum, posterior cerebral artery angle, 4th ventricle and the aqueduct of Sylvius.5–8 However, there are only two reported cases of intracisternal cysts, namely in the premedullary9 and basal cisterns.3 The hydatid cysts reported here were localized in the right cerebellopontine cistern and we confirmed their intracisternal location during the operation. In the cerebral cisterns, the most likely pathway of dissemination is haematogenous spread to the meninges and rupture of a primary cyst into the subarachnoid space.3 Magnetic resonance imaging is the best choice to diagnose a hydatid cyst. On MRI, the signal from the cyst is nonhomogeneous: iso- or hypointense on T1-weighted and hyperintense on T2-weighted images. Compared to CT scan, MRI is more reliable for detecting the irregularities at the rim border. In addition, MRI can estimate the thickness of the rim. The pericyst shows contrast enhancement. The sensitivity of MRI together with its multiplanar imaging capabilities, allows for accurate detection, localization and assessment of affected structures and for infratentorial hydatid lesions, the relationship with cranial nerves and vascular architecture are visualized more precisely.1,2,9–11
396
Case reports / Journal of Clinical Neuroscience 14 (2007) 396–398
Regarding the differential diagnosis of hydatid cysts, arachnoid cysts and epidermoids are common in the cerebellopontine cisterns.7 Cystic astrocytomas, porencephalic cysts and pyogenic or fungal abscesses are other lesions to be differentiated.2 Epidermoid cysts, being the third most common cerebellopontine angle tumor, usually have slightly hyperintense signal intensity on proton density MRI. These lesions usually surround neighboring nerves and vessels, whereas arachnoid and hydatid cysts displace adjacent structures.8 The differential diagnosis of meningioma, hemangioma, glomus tumor, cystic astrocytomas and abscesses may be confirmed by the absence of a mural nodule, perifocal edema and contrast enhancement. Arachnoid cysts and porencephalic cysts do not show contrast enhancement as much as hydatid cysts. On the other hand, diffusion MRI is not very useful because both hydatid and arachnoid cysts show increased diffusion.1,2 The treatment of choice for supratentorial cerebral hydatid cyst is cautious surgical removal without rupture. This is more difficult when the hydatid cyst is located in the cerebellopontine cisterns, as the cranial nerves and vascular structures in this region are tightly adhered to the hydatid cyst membrane and if cyst is removed without microdissection, it may result in neural and vascular harm as well as unexpected rupture. In conclusion, MRI is a valuable diagnostic technique to visualize cisternal hydatid cysts and to differentiate them from other cystic lesions and tumors. MRI can precisely define the relationship of the cyst with the vascular and neural
structures, as well as the jugular foramen and the internal acoustic canal which is important in pre-operative planning. References 1. Abbassion K, Amirjamshidi A. Diagnosis and management of hydatid cyst of the central nervous system: Part 1: General considerations and hydatid disease of the brain. Neurosurg Q 2001;11:1–9. 2. Ersahin Y, Mutluer S, Gu¨zelbag E. Intracranial hydatid cyst in children. Neurosurgery 1993;33:219–25. 3. Tistouridis J, Dimitriadis AS, Kazana E. MR in cisternal hydatid cysts. AJNR Am J Neuroradiol 1997;18:1586–7. 4. Altıno¨rs N, Bavbek M, Caner HC, et al. Central nervous system hydatidosis in Turkey: a cooperative study and literature survey analysis of 458 cases. J Neurosurg 2000;93:1–8. 5. Villarejo F, Blazquez MG, Arcas J, et al. Hydatid cyst of the posterior fossa: case report. Neurosurgery 1983;12:228–9. 6. Akdemir G, Ergu¨n R, Gezici AR, et al. Multiple hydatid cyst of aqueduct of Sylvius. Case report with MR Imaging study. Turk Neurosurg 2000;10:142–4. 7. Mascalchi M. Pontine hydatid cyst in association with an acoustic neurinoma. MR appearance in an unusual case. AJNR Am J Neuroradiol 1991;12:190–3. 8. Vaquero J, Jimenez C, Martinez R. Growth of hydatid cysts evaluated by CT scanning after presumed cerebral hydatid embolism. J Neurosurg 1982;75:837–8. 9. Rumboldt Z, Jednacak H, Talan-Hranilovic J, et al. Unusual appearance of a cisternal hydatid cyst. AJNR Am J Neuroradiol 2003;24: 112–4. 10. Von Sinner WN, Strake TEL, Clark D, et al. MR imaging in hydatid disease. AJR Am J Roentgenol 1991;157:741–5. 11. Tien RD, Macfall J, Heinz ER. Evaluation of complex cystic masses of the brain: value of steady-state free-precession MR imaging. AJR Am J Roentgenol 1992;159:1049–55.
doi:10.1016/j.jocn.2006.04.007
Quetiapine successfully treating oculogyric crisis induced by antipsychotic drugs Philippos Gourzis a b
a,*
, Panagiotis Polychronopoulos b, Andreas A. Argyriou b, Elisabeth Chroni b, Stavroula Beratis a
Department of Psychiatry, University of Patras Medical School, Rion-Patras, Greece Department of Neurology, University of Patras Medical School, Rion-Patras, Greece Received 14 November 2005; accepted 22 April 2006
Abstract We report two patients who developed persistent oculogyric crisis, obsessional thoughts and psychiatric symptoms after prolonged treatment with typical and atypical antipsychotics. Both our patients did not improve after withdrawal of these antipsychotics, but rather after quetiapine was administered. 2006 Elsevier Ltd. All rights reserved. *
Corresponding author. Tel.: +30 2610 999 728; fax: +30 260 994 534. E-mail address: [email protected] (P. Gourzis).