Precentral Knob Corresponds to the Primary Motor and Premotor Area

Abstract

Identification of the primary motor area (M1) using computerized tomography (CT) or magnetic resonance imaging (MRI) is critical to delineate the effect of various diseases (e.g., brain tumors, infarction, multiple sclerosis) as well as for the preoperative planning for patients undergoing resection of brain tumors. The utility of non-invasive identification of M1 using functional MRI (fMRI) has been demonstrated by comparing the location of M1 detected by fMRI with that by invasive and direct methods, such as intraoperative cortical mapping [1][2][3] . Recent studies suggest that the precentral knob is an anatomic landmark of the M1 4-13 . However, the location of precentral knob has never been compared with M1 as detected by invasive and direct methods, namely cortical mapping during awake surgery. Thus, ABSTRACT: Purpose: Cortical mapping during awake surgery assesses intraoperative neurological change in response to electrical stimulation to provide direct information regarding the anatomical localization of the primary motor area (M1). The goal of the present study was to analyze the reliability of the identification of the precentral knob in the axial image of magnetic resonance imaging or functional MRI (fMRI) for the detection of M1. Materials and Methods: Among patients with brain tumors within or near M1 in whom awake surgery was employed from April 2004 through March 2007, 14 cases were analyzed in which either the M1 or premotor area (PMA) was successfully detected by mapping during awake surgery. Results: The precentral knob was localized to the PMA in 4 cases and to M1 in 10 cases. By contrast, the gyrus activated by hand clenching in fMRI on the affected side at least partially corresponded to M1 in all cases, while those on the unaffected side corresponded to M1 in 12 of 12 cases. Conclusion: These results indicate that the precentral knob corresponds to PMA as well as to M1, whereas the gyrus activated in fMRI corresponds to M1 on the affected and unaffected side.

The reliability of neuroanatomy as a predictor of eloquence: a review

“…7,20,48,55 For example, the concept of the precentral knob representing the primary motor area of the hand has In this "average brain," patients' brains were linearly transformed into a common space using a 12-parameter affine transformation.…”

“…48 Others have reported variability in the functional organization of the primary sensorimotor cortices as well. For example, within the precentral gyrus, stimulation of individual cortical sites has been shown to recruit both sensory and motor phenomenon and in other cases stimulation has been shown to recruit motor movements in more than 1 motor group.…”

Advantages and disadvantages of awake surgery for brain tumours in the primary motor cortex: institutional experience and review of literature

“…1). 22 While other investigators have reported that the electrophysiological method of SEP can localise the M1, 28 our studies demonstrated that the M1 was successfully localised by SEP in only 6 of 16 patients with brain tumours involving the M1 (Table II). Thus, neither the inverted omega method nor SEP can reliably localise the M1 in all cases.…”

“…Thus, neither the inverted omega method nor SEP can reliably localise the M1 in all cases. 14,22 Removal of brain tumour involving the M1 without induction of new motor deficits In our series of patients undergoing awake surgery for resection of brain tumours involving the M1 study, slight deficits in postoperative motor function occurred in 4 of 21 cases (Table II). By contrast, transient deterioration of either upper or lower limb motor function was observed in 13 of 21 cases during the awake surgery itself (Table II).…”

“…Therefore, fMRI is the most reliable modality for localisation of M1 in patients with brain tumours involving the M1. 14,22,23 Cortical mapping is also associated with limitations. For example, cortical mapping has low sensitivity for the detection of motor function in proximity to brain tumours in the M1, and therefore using this modality for the intraoperative localisation of the M1 is difficult and time consuming.…”