Original Article

Intraoperative Ultrasound in Intracranial Space Occupying Lesions

Deepak Patil,  Vivek Sharma, V Divye Prakash Tiwari 

• ^*Department of Neurosurgery, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India

• Friday, November 01, 2013
• Sunday, November 03, 2013
• Thursday, November 14, 2013

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective

The aim was to assess the role of intraoperative ultrasound in intracranial space occupying lesion.

Methods

We have performed intraoperative ultrasound in 192 patients of cranial space occupying lesions admitted at our university hospital. Intraoperative ultrasound was performed by SonoSite, 180 plus hand carried ultrasound system with c11/7-4 Mhz curved array transducer probe. A preoperative Computed tomography or Magnetic resonance was performed in all patients. Preoperative and postoperative neurological function was assessed.

Observations

Intraoperative ultrasound examination is an excellent device in localizing the small intracranial space occupying lesion. It also helps in planning the durotomy and extending the craniotomy size if required. It helps in identifying the shortest and safest site to approach the lesion, and helps in preventing the damage to eloquent areas. In cases of cystic tumor with small solid component, it helps in guiding the cyst puncture and exact localization of the solid component. In cases of large intracranial space occupying lesions, post excision intraoperative ultrasound helps in delineating the completeness of resection. Residual tumor if seen in ultrasound was excised.

Conclusion:

Intraoperative ultrasound is portable and does not require any specialized setup. It is cost effective and provides real time images. It can be repeated as and when required during operation with minimum scanning time, and ensures patient and operator safety.

Keywords

Intraoperative ultrasound,glioma, meningioma,intracranial tumour, brain neoplasm

Introduction

Preoperative images in Magnetic Resonance Imaging (MRI) or Computerized Tomography (CT) data is commonly used for guidance during surgery. It is important to localize the tumour on the surface of brain so that unnecessary neural damage can be avoided. Thus per-operative ultrasound helps to a great extent but many different factors like drainage of cerebrospinal fluid, excision of tumor mass and position of the patient intraoperatively affect the tissue alignment and may cause problem called brain shift [1,5].

Intraoperative imaging modalities like intra operative ultrasound, intraoperative CT, and intraoperative MRI have been introduced to know real time images reflecting the true patient’s anatomy. Intraoperative ultrasound imaging of the brain is being performed usually by transducers with 5 or 7.5 MHz. The 5 MHz probe retains the ability to visualize up to the depth of 15 cm while 7.5 MHz probe is used for more superficial application [6]. Ultrasound waves do not propagate efficiently in air the space therefore saline is being used as acoustic medium between the surface of the transducer and the brain [7].

Patients and Methods

This study included 192 cases of cranial space occupying lesions who were admitted in the Department of Neurosurgery, Institute of Medical Sciences, Banaras Hindu University between 2011 to 2013. The mean age of the patients was 48 (+/- 28) years and the male to female ratio was 51 to 45. The detailed clinical history including name, age, sex, social status, history related to etiological factors, onset and duration of disease was taken. Thorough physical examination was performed. The Chief Complaints like headache, nausea, vomiting, seizures, dysphasia, loss of consciousness, cerebellar involvement-nystagmus, intentional tremor, unsteadiness of gait, cranial nerve involvement, limb weakness, behavioral changes were noted. Past history like previous operation and radiation, type of intervention and outcome of intervention were noted. Preoperative investigations like computerized tomography and magnetic resonance imaging were done. The Ultrasonography was performed at the beginning and end of operation.

Intraoperative Details

Intraoperative ultrasound (IOUS) with SonoSite, 180 plus with c11/7-4 Mhz curved array transducer probe was done in all cases. The ultrasound probe, covered with an aseptic sheath, was placed directly on the surface of the duramater exposed by craniotomy, and saline was used as acoustic coupling agent. The probe was manipulated on the examining surface to obtain coronal and sagittal views of the lesion through the window formed by the removal of bone. Intraoperative ultrasonographic findings like tumor location, cortical sulci above the tumor, depth of the tumor, relationship with the surrounding anatomical structures, and extent of resection at the end of surgery were noted.

Results

In our study majority of the patients (52.8%) were in the age group of 41-60 years and the average age was 52.8 year. There were 57 patients in the age group of 21-40 years, 37 patients in the age group of 0-20 years and 26 patients in the 61 years and above age group with mean age of 31.1, 9.6 and 66 respectively. The younger patient was 6 year old while the oldest was 73 year old. The male patients outnumbered the female counterpart (53.13% versus 46.87%). Supratentorial lesions accounted for 136 cases (70.83%) whereas infratentorial cases were 56 (29.17%). The supratentorial lesions were distributed in the frontal, temporal, parietal and occipital lobe in 52 (38.24%), 36(26.47%), 28 (20.59%) and 20(14.70%) respectively.

Intraoperative frozen section and postoperative histopathological findings confirmed the diagnosis. Meningioma accounted for the highest number of supratentorial cases (54,39.70%). High grade gliomas (Glioblastoma and Anaplastic Astrocytomas) accounted for maximum cases of gliomas (31,22.80%) whereas low grade gliomas were found in 20 cases (14.70%). Six out of 10 cases of abscess were tubercular (4.41%) while 4 (2.94%) were pyogenic. There were 10 cases of Metastasis (7.35%). The Hydatid cyst, Arachnoid cyst and Neurocysticercosis were reported in 4 (2.94%), 4 (2.94%) and 2 (1.47%) cases respectively. Among infratentorial ICSOLs, Acoustic neuroma/schwannoma accounted for maximum cases (11, 19.64). Pilocytic astrocytoma & Meningioma were reported in 10 cases each (17.86%). Medulloblastoma (6,10.71%), Ependymoma (6,10.72%), Metastasis(3,5.36%), Arachnoid cyst (3,5.36%), Neurocysticercosis (1,1.78%), Hemangioblastoma (2,3.57%) and Abscess (4,7.14%) were the remaining cases.

Among supratentorial (n=136), 95 cases underwent Gross tumor resection (69.85%), while subtotal resection and biopsy in 26 (19.12%) and 15 (11.03%) cases respectively. Among infratentorial group (n=56), 50 cases underwent gross tumor resection (89.29%). Subtotal resection and diagnostic biopsy was performed in 4 (7.14%) and 2 cases (3.57%).  (table 1)

Table 1: Completeness of resection (n=192)

Supratentorial (n=136)	No. of patients	Percentage
Gross tumor resection	95	69.85
Subtotal resection	26	19.12
Biopsy	15	11.03
Infratentorial (n=56)
Gross tumor resection	50	89.29
Subtotal resection	04	7.14
Biopsy	02	3.57

Among 41 supratentorial meningiomas on IOUS, all had clear delineation of border (100%), 38 were hyperechoic (92.68%) Figure 1 , 39 tumors had homogeneous interior (95.12%), 20 tumors had hypoechoic surrounding edema (48.78%).

Figure 1. Right parieto-occipital meningioma (a).preoperative CT Scan, (b).IOUS image showing tumor in relation to falx

Edema was absent in 15 cases (36.58%) and edema not defined in 6 cases (14.63%). Table 2.

Table 2: Analysis of 41 supratentorial meningiomas on IOUS (n=41)

Meningioma	No. of patients	Percentage
Clear delineation of border	41	100
Hyperechoic tumor	38	92.68
Homogeneous interior	39	95.12
Hypoechoic surrounding edema	20	48.78
No edema	15	36.58
edema not defined	06	14.63

Among 51 supratentorial Glioma on IOUS, 23 tumor were hyperechoic (45.10%) Figure 2, 19 had mixed echogenicity (37.25%) while 9 were hypoechoic (17.65%). Thirty two tumors had well defined border (62.74%) and 46 tumors had perifocal edema (90.20%). Table 3

Fig 2. A 28 years old male with left frontal glioma (a large cyst with small solid component) (a). preoperative CT scan, (b). MRI Axial, (c).Intraoperative ultrasound, (d).Intraoperative ultrasound postexcision

Immature abscesses had indistinct margin, irregular shape and variable echogenicity. Mature abscess had distinct margin, regular shape with hypoechoic nature. Cerebral neurocysticercosis had distinct margin, irregular shape with hyperechoic scolex in cyst. Arachnoid cyst was uniformly hypoechoic. Metastases were mostly homogeneous iso or hyperechoic well delineated lesions Figure 3. Hydatid cyst was uniformly hypoechoic.

Table 3:Site of Intracranial Lesion

Glioma	No. of patients	Percentage
Tumour hyperechoic	23	45.10
Mixed echogenicity	19	37.25
Tumour hypoechoic	09	17.65
Well defined border	32	62.74
Perifocal edema	46	90.20

Fig.3.Vermian metastatic adenocarcinoma (a).T2 MRI image, (b). Intraoperative Ultrasound

Lesions of the Posterior Fossa

Meningioma, Gliomas, Metastases, cysts had similar appearance as of their supratentorial counterpart. Cerebellopontine angle tumors were clearly visualized. IOUS of the posterior fossa was useful as a guide for tumor biopsies, and for the detection of small subcortical lesions. Hemangioblastoma in the cerebellum appeared as a hypoechoic cyst with hyperechoic small mural nodule on IOUS.

Discussion

Solheim et al, (2010) published a series of 156 malignant gliomas: 142 (91%) were resected while 14 (9%) were undergone biopsies. [8] They reported gross total resection (GTR) in 37% of all high-grade glioma resection. Chacko et al, (2003) evaluated thirty-five patients with parenchymal brain lesions including 11 low-grade and 22 high-grade tumours and 2 inflammatory granulomata. [9]. They found all tumours irrespective of histology to be hyperechoic on IOUS. In 71.4% of cases, IOUS was useful in defining their margins, however in the remaining cases the margins were illdefined. Wang et al, (2011) evaluated 52 patients with small subcortical lesion. [10].In our study we found that IOUS examination is excellent in localizing small intracranial space occupying lesions. In 30 cases of gliomas we also performed tumor localization with neuronavigation. Before durotomy neuronavigation was fairly accurate in localizing the gliomas matching the IOUS localization. However after durotomy and resection of tumors with alteration in tissue dynamics with cerebrospinal fluid loss, tumor tissue loss, neuronavigation proved inaccurate in 19 cases because of brain shift. We found that IOUS helps in planning the durotomy and if needed extending the craniotomy. It helps in identifying the shortest and safest approach to the lesion and helps in preventing damage to vital areas. In cases of cystic tumors with small solid component, IOUS helps in guiding the cyst puncture and exact localization of the solid component. In cases of large intracranial space occupying lesions post excision intraoperative ultrasound helps in delineating the completeness of resection. Residual tumor if left was excised. Neurosurgeons who have used real time 2D ultrtasound for different procedures, have found 3 D ultrasound cumbersome because the probe comes on the way of instruments. Special attention must be paid to positioning the surgical instrument accurately in the real time 2D US scan plane to see and guide the surgical instrument in the image. In addition, extra space is needed in the craniotomy for simultaneous placement of both the US probe and the instrument. The main drawbacks of intraoperative CT are the huge amount of radiation exposure to the patient during surgery, escalation of radiation exposure with repeated imaging, additional radiologic staff dedicated for intraoperative purposes and the exorbitant cost related to build an intraoperative brain suite that will not be available at many institutions especially in developing countries. The main difficulties with the use of intraoperative MRI are requirement of non-ferromagnetic instruments, MR-compatible devices including operating microscope, additional technician & dedicated neuroradiologist experienced in intraoperative MR images as intraoperative MR images are different from pre- or postoperative ones because of the air-brain-interface and changes due to surgical manipulation e.g. blood clots. An additional 60 to 90 minutes of anesthesia time is needed. The transfer to intraoperative MRI suite is cumbersome and repeated imaging at different stages of operation if needed is not feasible. IOUS is a cheaper solution and it is safe for both the patient and operator.

Conclusion

IOUS is portable, does not require any specialized setup, provides real time images, cost effective, and can be repeated as and when required during the procedure with minimum scanning time. It also ensures patient and operator safety. IOUS can be performed without increasing operation time significantly. It might even shorten it because it increases the surgeons’ feeling of safety.

Authors' Contribution

DP: Collection of data, and preparation of the manuscript.
VS: Concept and design, preparation of the manuscript.
DPT: Literature review and preparation of the manuscript.
All authors have read and approved the final manuscript for publication.

Conflict of Interests

The authors declare that there are no conflict of interests.

Ethical Considerations

This is a retrospective review and is exempted from Ethical Committee review.

Funding

None declared

Acknowledgement

None

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