A taxonomy for brainstem cavernous malformations: subtypes of pontine lesions. Part 1: basilar, peritrigeminal, and middle peduncular

Abstract

OBJECTIVE Brainstem cavernous malformations (BSCMs) are complex, difficult to access, and highly variable in size, shape, and position. The authors have proposed a novel taxonomy for pontine cavernous malformations (CMs) based upon clinical presentation (syndromes) and anatomical location (findings on MRI). METHODS The proposed taxonomy was applied to a 30-year (1990–2019), 2-surgeon experience. Of 601 patients who underwent microsurgical resection of BSCMs, 551 with appropriate data were classified on the basis of BSCM location: midbrain (151 [27%]), pons (323 [59%]), and medulla (77 [14%]). Pontine lesions were then subtyped on the basis of their predominant surface presentation identified on preoperative MRI. Neurological outcomes were assessed according to the modified Rankin Scale, with a score ≤ 2 defined as favorable. RESULTS The 323 pontine BSCMs were classified into 6 distinct subtypes: basilar (6 [1.9%]), peritrigeminal (53 [16.4%]), middle peduncular (MP) (100 [31.0%]), inferior peduncular (47 [14.6%]), rhomboid (80 [24.8%]), and supraolivary (37 [11.5%]). Part 1 of this 2-part series describes the taxonomic basis for the first 3 of these 6 subtypes of pontine CM. Basilar lesions are located in the anteromedial pons and associated with contralateral hemiparesis. Peritrigeminal lesions are located in the anterolateral pons and are associated with hemiparesis and sensory changes. Patients with MP lesions presented with mild anterior inferior cerebellar artery syndrome with contralateral hemisensory loss, ipsilateral ataxia, and ipsilateral facial numbness without cranial neuropathies. A single surgical approach and strategy were preferred for each subtype: for basilar lesions, the pterional craniotomy and anterior transpetrous approach was preferred; for peritrigeminal lesions, extended retrosigmoid craniotomy and transcerebellopontine angle approach; and for MP lesions, extended retrosigmoid craniotomy and trans–middle cerebellar peduncle approach. Favorable outcomes were observed in 123 of 143 (86%) patients with follow-up data. There were no significant differences in outcomes between the 3 subtypes or any other subtypes. CONCLUSIONS The neurological symptoms and key localizing signs associated with a hemorrhagic pontine subtype can help to define that subtype clinically. The proposed taxonomy for pontine CMs meaningfully guides surgical strategy and may improve patient outcomes.

Mandibular Fossa Approach to Petroclival and Anterior Pontine Lesions

“…She had a giant pontine cavernous malformation occupying the entire pons (termed “holopontine”), classified primarily as a basilar pontine subtype. 11 This lesion had a pial presentation inferomedial to CN V on the right ( Fig. 5A–C ).…”

A taxonomy for brainstem cavernous malformations: subtypes of pontine lesions. Part 2: inferior peduncular, rhomboid, and supraolivary

“…This study reports the nuances of pontine subtypes 4-6 (IP, rhomboid, and supraolivary), building on our effort to establish an anatomical BSCM taxonomy as described in detail in Part 1 of this series. 2 The taxonomy is intended to guide the selection of surgical approaches and resection strategies. Our study also confirms that the constellations of neurological symptoms and signs of the hemorrhagic BSCM subtypes help to define these clinical subtypes even before pathological anatomical findings FIG.…”

“…The locations of the 6 subtypes are shown in the inset: 1) basilar (teal), 2) peritrigeminal (red), 3) middle peduncular (orange), 4) IP (green), 5) rhomboid (purple), and 6) the more inferiorly located supraolivary subtype ghosted through the pons (yellow). The IP, rhomboid, and supraolivary subtypes are featured in this article (Part 2 of this 2-part series), whereas the basilar, peritrigeminal, and middle peduncular subtypes (1)(2)(3) ference between mRS score at preoperative baseline and that at the last available postoperative examination, with good outcome defined as unchanged or improved mRS score and poor outcome defined as worsened mRS score. Statistical significance was defined as p ≤ 0.05.…”

“…Descriptions of subtypes 1-3 are provided in greater detail in Part 1 of this 2-part series. 2 In brief, of 323 patients with pontine BSCMs (mean ± SD age 41.2 ± 14.2 years; 197 [61%] female patients; 126 [39%] male patients), most (310 of 323 patients [96%]) presented with symptomatic hemorrhage. 2 Of the 178 patients with pontine lesions who had Lawton BSCM grades available, 66 (37%) had low-grade BSCMs (grades 0-II), 100 (56%) had intermediate-grade BSCMs (grades III-V), and 12 (7%) had high-grade BSCMs (grades VI and VII) (Table 1).…”

“…In brief, the pons lies between the midbrain and medulla and is the largest of the 3 brainstem parts. 1,2 It is the most common site of brainstem cavernous malformations (BSCMs) 3 and accounts for about 60% of such lesions in our experience. Approaches to pontine CMs are based on the location where the lesion presents to a pial or ependymal sur-face.…”