The Yin and Yang of Operating on a Posterior Fossa Meningioma: The Schmahmann Syndrome
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.355121
Source of Support: None, Conflict of Interest: None
Keywords: Behavioral disturbances, cerebellar cognitive affective syndrome, pathological laughter, posterior fossa meningioma, Schmahmann syndrome
The cerebellum has been classically associated with regulation of coordination, balance, and movement. Although there have been anecdotal reports of behavioral anomalies in association with cerebellar disorders, little is known or described. Early reports were not pathologically verified, and a possibility of cerebellar contribution to non-motor functions was largely dismissed.
The cerebellar cognitive affective syndrome (CCAS), described as Schmahmann syndrome, was first reported in 1998. Since then, there has been an increasing awareness of the pattern of cognitive deficits that may occur in association with an isolated cerebellar pathology. These cognitive non-motor deficits result in an overall lowering of intellectual function and are believed to be caused by a dysfunction of cerebellar connections to the cerebral cortex and limbic system.
There is still a paucity of published literature and awareness regarding this clinical entity. Most of these cases have been reported in patients with cerebellar infarcts or congenital cerebellar pathologies. We present the first report of the Schmahmann syndrome occurring in a patient following the excision of a tentorial meningioma and discuss the relevant pathophysiology.
A 35-year-old lady presented with complaints of progressively increasing occipital headache for 1 year. She developed hearing loss and tinnitus in the right ear along with mild gait ataxia 3 months back. On examination, she had sensorineural hearing loss, absent gag reflex, and cerebellar signs on the right side. She showed no specific cognitive deficits apropos of her level of education (Hindi Mental Status Examination score 28/31).
Magnetic resonance imaging (MRI) demonstrated a large (5 × 4 × 4 cm) posterior fossa meningioma. The lesion was compressing the right cerebellar hemisphere, middle cerebellar peduncle, and right transverse sinus. A provisional diagnosis of tentorial meningioma was made [Figure 1]a, and she underwent a right suboccipital craniotomy and near-total excision of the tumor. Intraoperatively a tiny part of the tumor invading the transverse sinus was left behind. Histopathological examination was consistent with the clinical diagnosis and showed transitional meningioma (WHO Grade-I).
Her immediate postoperative period was uneventful. A routine postoperative contrast MR showed gross-total excision of tumor [Figure 1]b. Fluid-attenuated inversion recovery and diffusion-weighted sequences suggested acute infarct involving the right posterosuperior cerebellar hemisphere and ipsilateral superior vermis probably secondary to a cortical branch of superior cerebellar artery (SCA) injury [Figure 1]c, [Figure 1]d, [Figure 1]e. No active intervention was done in the immediate postsurgical period since the patient was clinically stable.
On postoperative day 5, she started having cognitive and behavioral abnormalities. She developed abnormal aggressive, impulsive behavior, irrelevant talk, and emotional lability, including crying and laughing without reason. The attendants noticed disturbances in her sleep cycle and verbal aggression directed against family members. There were no new motor deficits. Subtle cerebellar motor signs were present, as expected in the postoperative period, after the excision of a large posterior fossa lesion. Her electrolytes and other metabolic parameters were within normal limits.
A formal psychiatric evaluation was done. Although she was aware of her surroundings and comfortable, she appeared inappropriately cheerful. She was copying the interviewer's actions during the examination and was easily distractible. Her judgment was impaired (sitting on the bed with her footwear on) and had a poor insight (Grade-1). Her symptoms corroborated with CCAS, and we used the CCAS scale to characterize her behavioral and cognitive deficits. She failed multiple tests described in this grading scale [Table 1] and had a “Definite CCAS” as per the findings [Figure 1]f. She was managed with conservative treatment, including mood stabilizers. At a 6-month follow-up, her symptoms have improved to a great extent.
Contemporary neurological teaching still describes the cerebellum as a part of the brain which plays an essential role in performing the precise, coordinated movements. However, as our knowledge about the circuitry and functioning of the brain continues to improve, we have come to realize that the cerebellum has more to it than just coordination of motor movements. Schmahmann et al. published an unprecedented work in this area, proving with clinical-neuropsychological and radio-anatomical studies that cerebellum does play an essential role in cognition and affect.
Schmahmann syndrome, a clinical diagnosis, typically has four distinct groups of symptoms—(a) impairment of executive functions, such as planning, set-shifting, verbal fluency, abstract reasoning, and working memory, (b) impaired visuospatial cognition, (c) personality and behavior changes with blunting of affect or abnormal crying/laughter, and (d) language deficits including agrammatism and word-finding disturbances.,, However, all four complexes of symptoms need not be present in every patient of CCAS.
It is believed that there is functional compartmentalization in the cerebellum due to specific input and output pathways for each cerebellar anatomical region. The complex of neurocognitive and behavioral symptoms described with cerebellar pathologies are thought to arise due to functional disruption of “reciprocal pathways” that connect posterior lobe/vermis of the cerebellum with the limbic system and prefrontal association cortices. These pathways consist of a feed-forward limb via corticopontine/pontocerebellar pathways and a feedback limb via cerebellothalamic and thalamocortical systems. Posterior lobe damage has explicitly been implicated in the pathogenesis of CCAS, and a vermis lesion has been linked to a disruption in affect and speech.
Another related cerebellar disorder affecting the behavior of the patient is the “cerebellar mutism syndrome” (PFS). This syndrome may be considered a semiological subtype of CCAS wherein the children with midline posterior fossa tumors suffer behavioral and speech abnormalities after vermis resection., We have earlier described the occurrence of behavioral abnormalities – inappropriate pathological laughter in patients with severe midbrain compression due to petroclival tumors.,,, The etiology of this abnormal inappropriate laughter/crying due to midbrain compression may involve compression of the same fibers in the midbrain of the feed-forward pathway, as described earlier. We propose that these three disorders affecting the behavior and personality of patients—namely CCAS, PFS, and inappropriate laughter/crying due to midbrain compression—are all part of a continuum of disorders in which either the posterior lobe or vermis of the cerebellum is lesioned, or its connections with cerebral cortex are altered in some way.
Although, past studies have found CCAS in patients with posterior circulation stroke (posterior inferior cerebellar artery, anterior inferior cerebellar artery and SCA stroke),, postinfectious cerebellitis, midline/vermian tumors post-resection, and developmental malformations of cerebellum such as Joubert syndrome, we found no published report of CCAS developing after resection of an extra-axial tumor-like meningioma. It would be presumptive to conclude that only the SCA territory stroke led to these symptoms in our case, because not every SCA territory stroke leads to Schmahmann syndrome. Whether it was the excision of the meningioma with the consequent decompression of the cerebellar tissue which had been compressed for a long time, or merely the SCA territory stroke secondary to operative handling, is difficult to prove. Even if we assume that the SCA branch injury or thrombosis may have led to these symptoms, this syndrome's occurrence after posterior fossa meningioma has not been reported before and we think it is an important complication to know especially for a neurosurgeon so that patients can be better counseled while taking an the informed consent.
The cerebellum is now considered a crucial modulator of neurocognitive and affective processing through an integrated network of cerebellar-cerebral connections. The occurrence of CCAS, PFS, and behavioral abnormalities provide further clinical evidence of the affective functions of the cerebellum modulated mainly by the posterior lobe and vermis of the cerebellum.
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