Tectal plate tumors

Tumores da região tectal

Tectal plate tumors

Tumores da região tectal

Bruno C.R. Lázaro^I; José A. Landeiro^II

^IDepartment of Neurosurgery, Brazilian Air Force Hospital, Rio de Janeiro, RJ, Brazil

^IIM.D., Ph.D, Head of Department

ABSTRACT

Tectal plate is a rare location for a tumor. Many papers have described different types of pathology arising in that location including tumors, vascular lesions, inflamatory and infectious processes. In this paper we describe our experience in treating seven patients with tectal plate lesions, with different ages and types of pathology: five patients presented with low grade gliomas, one with lung cancer metastasis and the last presenting with a tectal plate cavernoma. Open surgery was performed in three cases (due to tumor enlargement or need for the exact diagnosis). In the other cases, the treatment of non-comunicating hydrocephalus was the only treatment employed. The prognosis is of course dependent on the underlining pathology. In our series, except in the metastatic tumor case and the cavernoma, the other types of lesion consisted of low grade gliomas. These lesions represent a different type of brain stem tumor sharing a common good prognosis, with a benign behavior. We believe that tectal tumors must be managed case by case. When a patient presents with a benign lesions in the tectal region, treating the main symptom – hydrocephalus - should be the first attempt in management of these lesions.

Key words: brain stem, tectal tumors, brain stem tumors, third ventriculostomy.

RESUMO

Tumores na região do teto mesencefálico são raros. Vários tipos de lesões como tumores, lesões vasculares, inflamatórias e infecciosas localizam-se nesta região. Nós revimos o tratamento adotado em sete pacientes com diferentes tipos de lesões tectais: cinco pacientes apresentando gliomas de baixo grau, um paciente com lesão metastática proveniente de câncer de pulmão e um com cavernoma. O tratamento cirúrgico com abordagem direta da lesão foi realizado em três casos (devido ao aumento do volume tumoral ou quando houve necessidade da confirmação diagnóstica). Nos demais casos o tratamento para a hidrocefalia não-comunicante foi o método empregado. O prognóstico dessas lesões é baseado no tipo de patologia em questão. Em nossa série, com exceção do caso de metástase e do paciente com cavernoma, as demais lesões foram gliomas de baixo grau. Estas lesões representam um subgrupo diferenciado de tumores de tronco encefálico, apresentando bom prognóstico e tendo comportamento benigno com sobrevida elevada. Acreditamos que tumores da região tectal devam ser avaliados caso a caso. Na hipótese diagnóstica de uma lesão benigna, o tratamento do principal complexo sindrômico – hidrocefalia não-comunicante – é provavelmente a melhor conduta a ser empregada.

Palavras-chave: tronco cerebral, tumores da região tectal, ventriculostomia.

Brain stem tumors are a wide described pathology. Most of the papers avaiable in the literature are of interest to the pediatric group. In general, it is accepted that brain stem tumors account for approximately 10-30% of brain tumors in children^1-10. In these cases, three main groups are identifiable, according to location and prognosis. Diffuse pontine is the largest subgroup carryng a worst prognosis with a median survival of approximatelly one year; slow growing low grade gliomas comprise the second subgroup, arising at the cervicomedullary junction or from the floor of the 4^th ventricle baring a long survival rate - almost more than 5 years. The third subgroup is represented by focal tectal gliomas¹.

On the other hand, brain stem tumors in adults - especially gliomas - are poorly understood in terms of low incidence and different pattern of behavior. Over all, it is actually observed that the prognosis of brain stem tumors is better in adults than in children. The peak incidence prevailed in the third and fourth decade in adults and in the first decade in children². Among tumors found in the tectal plate, the most common is the astrocytoma, but other types have been described, such as oligodendroglioma, ependymoma, ganglioglioma, medulloblastoma³, primitive neuroectodermal tumors, metastasis; as well as lipoma¹¹, melanoma¹², dysembryoplastic neuroepitelial tumor (DNT)¹³, cavernomas, abscess and periaqueductal gliosis.

We present seven cases of tumors arising in the tectal plate managed in our institution.

METHOD

We present seven cases of patients with mesencephalic tectal plate tumors treated in our institution, in a retrospective analysis, between 1994 – 2005. There are 3 male and 4 female patients in this group with ages comprising 17 to 70 years-old.

Five patients presented Parinaud syndrome; all cases presented with noncommunicating hydrocephalus. Image studies were performed in all cases involving computed tomography scan (CT) and magnetic ressonance image (MRI) demonstrating lesions with the aspect of a low grade glioma in five cases, one case of high grade tumor (lung cancer metastasis), and the other presenting a vascular lesion (cavernoma).

The follow up period was over 8 years (1 to 8 years in average); open surgery was performed in 3 cases - 2 cases (see ilustrative cases below), cavernoma and the metastasis case - obtaining a definitive diagnosis; third ventriculostomy was performed in the other five cases (Table); in one case two procedures were necessary (see ilustrative cases below). There was one death – the metastatic tumor due to progressive disease (Table).

Ilustrative cases

Case 1 – A 26-year-old woman presented to our hospital with headache, nausea, papilledema and visual blurring. The CT scan revealed a noncommunicating hydrocephalus and a hypodense lesion on the tectal region (Fig 1). MRI demonstrated a tectal plate lesion (Fig 2) with lack of contrast enhancement.

She initially underwent ventricular-peritoneal shunt placement achieving adequate control and improvement of the symptoms, returning to normal activities and work afterwords.

One year later she returned to neurosurgical care presenting with worsening of the symptoms associated with incomplete Parinaud syndrome. A new MRI was performed and showed hydrocephalus and an increase of the lesion size (Fig 3). The shunt appeared to be malfunctioned. The tumor was removed using the semi-sitting position achieving a gross total removal of the lesion, as presented in MRI (Fig 4). She experienced an improvement of the symptoms, being discharged from the hospital one week later.

Histopatological analysis revealed a grade II astrocytoma.

Case 2 – A 24-year-old man was admitted with a history of somnolence, disorientation, headache and Parinaud syndrome. He had undergone placement of a ventricular-peritoneal shunt 10 years before in another hospital for a diagnosis of "hydrocephalus" (history collected from his mother). A CT scan was performed showing a noncomunicating hydrocephalus. MRI was performed corroborating the diagnosis showing a T1 hypointense lesion located at the tectal plate.

He underwent an endoscopic third ventriculostomy with an imediate post opperative improving of the symptoms; the Parinaud syndrome was the last feature to disappear, occuring after one month. One year later he had reccurrence of the symptoms. A new radiologic study was performed showing once again a non-communicating hydrocephalus but the average size of the tectal tumor remained the same. A second third ventriculostomy was performed improving the symptomatology. He was discharged from the hospital 5 days after the procedure without symptoms (Fig 5).

DISCUSSION

In comparison to children, brain stem gliomas in adults is a less understood disease and present a much lower incidence (<2% of gliomas)¹. The survival rate however can be very much longer with the peak incidence in the third and fourth decades². The duration of symptoms is generally shorter in children while in adults it tends to be longer with tectal tumors, fourth ventricle dorsally exophytic tumors and cervicomedullary gliomas having a more favorable prognosis when compared to difuse lesions.

Tectal plate gliomas have been reported as a particulary indolent lesion often remaining stable in size for many years. The majority of these lesions were described as low grade gliomas, presented with late-onset aqueductal stenosis often without associated brain stem signs⁸. The average age at the time of diagnosis is about 10 years in children, with the majority of cases presenting with raised intracranial pressure secondary to obstruction of the Sylvian aqueduct¹⁴, with some other cases presented with Parinaud syndrome¹⁵ like the patients observed in our ilustrative cases, although this is also an uncommon feature. Even before the development of computed tomography, tectal tumors were an unrecognized because of late onset hydrocephalus⁶, once said that this can be the smallest lesion that can lead to death of the patient.

The radiologic investigation of these tumors have been up graded in the CT scan era with better visualization of the tectal region; but the majority of lesions continue to appear as noncommunicating hydrocephalus alone, although calcification or a hypodense lesion on the tectal plate can be observed. MRI of these tumors reveals tectal distortion or thickning caused by a localized mass, leading to aqueductal compression and hydrocephalus¹⁶; characteristic T1 hypointensity and T2 hyperintensity^17-21. MRI is an accurate and noninvasive method of diagnosis that can be indicated in all cases of late onset hydrocephalus and aqueductal obstruction, especially in adults. Even when present, contrast enhancement after gadolinium injection was an independent factor of tumor grading¹⁷.

The characteristics of the lesion seen on the MRI is of course dependent on its pathologic basis. In our series we presented 5 cases of patients baring a tectal low grade glioma, with the typical MRI appearence just as described above. The other two cases – a brainstem metastasis and a tectal plate cavernoma - appeared as an irregular enhancing lesion and a small vascular-like lesion presenting an impregnation of hemossiderin, respectivelly.

The prognosis of tectal plate lesion is a much debated issue in neurosurgical publications. It is reasonable to expect that a malignant lesion, brain stem metastasis and rapidally infiltrating lesions present a poor prognosis. But even in cases of tectal gliomas some controversies had arise.

Initially the pathology of intrinsic tectal lesions were considered to be similar to other brainstem tumors. In fact this was later discovered as not true. Many papers have oriented the presence of this tumor as a special site of low grade gliomas^4-6,9,10,18 . These tumors appear to present a better prognosis given to a slow growing rate and boundaries displacement instead of an infiltrative behaviour. However, the management of the patients remains controversial. The majority of authors oriented the management including a mandatory histopatological analysis to acertain the low grade mark, and just afterwords the adequate treatment is traced. We think that the conjunction of history, age, neuro exam and MRI appearence of a tectal lesion can be very suspicious for a low grade tumor. In our cases, there is a tendency for treating the symptom – usually noncommunicating hydrocephalus – as the first option, but it is not always possible when there is a high suspicion of another type of tectal lesion, like the cavernoma and the lung cancer metastasis cases in our series.

Surgical treatment consists on tumor resection or open biopsy; generally the surgical approach is that described for pineal region lesions, like the suboccipital-transtentorial or supracerebellar-infratentorial approach, prefered by this paper´s senior author and routinelly performed in this institution adopting the semi-sitting position.

Ultimatelly, with the advance of neuroendoscopy, a new perspective in dealing with these lesions had arisen. When the objective is to treat the hydrocephalus, a rigid endoscope can be utilized to perform a third ventriculostomy, as we described, with no major technical complications; the visibility of the inner surface of the third ventricle, with all structures involved is very good²².

Tectal tumors may extrude from the tectum into the lumen of the cerebral aqueduct and subsequently protrude to the third ventricle, pushing away the posterior commissure and enlarging the orifice. Some authors consider this lesion as intraventricular ones, treating each lesion individually²³.

With the advent of the flexible neuroendoscope other types of therapy could be performed. Potential treatment options include shunt placement²⁴ and aqueductal plasty^24,25. The third ventriculostomy success and failure rate is similar to those cerebral-spinal fluid (CSF) shunts – about 30%²⁴.

In conclusion, tectal tumors represent a differentiated category in neuro-oncology. Despite a variety of lesion encountered in this region, most publications indicate that low grade glioma is most prevalent. However, the major difficulty is regarding the adequate treatment of these lesions. A number of articles orients an invasive approach consisting of surgical treatment, given the need for mass reduction or just to obtain histopatological sample^5,27,28; other authors decline to conservative treatment, justified by the benign behavior and slow growth of this tumors^{4,6,8,19,29,30}. In our institution, the decision depends on individual analysis. We give preference in treating the major symptom – hydrocephalus – with CSF shunts or preferably endoscopic third ventriculostomy. Our study demonstrate that surgery should be indicated when there is evidence of tumor enlargement or in cases when the definitive diagnosis is imperative.

Acknowledgement – We thank Igor de Castro M.D for editorial assistance and José Francisco Salomão M.D. for his support

Received 4 October 2005, received in final form 16 January 2006. Accepted 17 February 2006

Dr. José A. Landeiro - Brazilian Air Force Hospital - Estrada do Galeão 4101 - Rio de Janeiro RJ - Brasil. E-mail: [e-mail]

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Publication Dates

• Publication in this collection
  02 Aug 2006
• Date of issue
  June 2006

History

• Reviewed
  16 Jan 2006
• Received
  04 Oct 2005
• Accepted
  17 Feb 2006