Intention tremor and olivary enlargement: clinico-radiological study

Holmes tremor: a delayed complication after resection of brainstem cavernomas

OBJECTIVE

In this paper, the authors aimed to illustrate how Holmes tremor (HT) can occur as a delayed complication after brainstem cavernoma resection despite strict adherence to the safe entry zones (SEZs).

METHODS

After operating on 2 patients with brainstem cavernoma at the Great Metropolitan Hospital Niguarda in Milan and noticing a similar pathological pattern postoperatively, the authors asked 10 different neurosurgery centers around the world to identify similar cases, and a total of 20 were gathered from among 1274 cases of brainstem cavernomas. They evaluated the tremor, cavernoma location, surgical approach, and SEZ for every case. For the 2 cases at their center, they also performed electromyographic and accelerometric recordings of the tremor and evaluated the post-operative tractographic representation of the neuronal pathways involved in the tremorigenesis. After gathering data on all 1274 brainstem cavernomas, they performed a statistical analysis to determine if the location of the cavernoma is a potential predicting factor for the onset of HT.

RESULTS

From the analysis of all 20 cases with HT, it emerged that this highly debilitating tremor can occur as a delayed complication in patients whose postoperative clinical course has been excellent and in whom surgical access has strictly adhered to the SEZs. Three of the patients were subsequently effectively treated with deep brain stimulation (DBS), which resulted in complete or almost complete tremor regression. From the statistical analysis of all 1274 brainstem cavernomas, it was determined that a cavernoma location in the midbrain was significantly associated with the onset of HT (p < 0.0005).

CONCLUSIONS

Despite strict adherence to SEZs, the use of intraoperative neurophysiological monitoring, and the immediate success of a resective surgery, HT, a severe neurological disorder, can occur as a delayed complication after resection of brainstem cavernomas. A cavernoma location in the midbrain is a significant predictive factor for the onset of HT. Further anatomical and neurophysiological studies will be necessary to find clues to prevent this complication.

Three-dimensional microsurgical anatomy and the safe entry zones of the brainstem

BACKGROUND

There have been no studies of the structure and safe surgical entry zones of the brainstem based on fiber dissection studies combined with 3-dimensional (3-D) photography.

OBJECTIVE

To examine the 3-D internal architecture and relationships of the proposed safe entry zones into the midbrain, pons, and medulla.

METHODS

Fifteen formalin and alcohol-fixed human brainstems were dissected by using fiber dissection techniques, ×6 to ×40 magnification, and 3-D photography to define the anatomy and the safe entry zones. The entry zones evaluated were the perioculomotor, lateral mesencephalic sulcus, and supra- and infracollicular areas in the midbrain; the peritrigeminal zone, supra- and infrafacial approaches, acoustic area, and median sulcus above the facial colliculus in the pons; and the anterolateral, postolivary, and dorsal medullary sulci in the medulla.

RESULTS

The safest approach for lesions located below the surface is usually the shortest and most direct route. Previous studies have often focused on surface structures. In this study, the deeper structures that may be at risk in each of the proposed safe entry zones plus the borders of each entry zone were defined. This study includes an examination of the relationships of the cerebellar peduncles, long tracts, intra-axial segments of the cranial nerves, and important nuclei of the brainstem to the proposed safe entry zones.

CONCLUSION

Fiber dissection technique in combination with the 3-D photography is a useful addition to the goal of making entry into the brainstem more accurate and safe.

Lesions in the central tegmental tract in autopsy cases of developmental brain disorders

We retrospectively analyzed central tegmental tract (CTT) lesions in 120 consecutive autopsy cases of developmental brain disorders to investigate the significance of symmetrical CTT lesions. Magnetic resonance imaging (MRI) findings of CTT lesions have been sporadically reported in various cases of child neurological diseases. In this study, symmetrical CTT lesions were observed in 25 (20.8%) among 120 cases of developmental brain disorders. These 25 cases were classified into three groups (groups I-III) in decreasing order of the severity of the lesion. Compared to five cases of group I in which CTT lesions were accompanied by diffuse tegmental damage, 20 cases of groups II or III developed relatively selective CTT lesions in which the medial longitudinal fasciculus and/or medial or lateral lemniscus were preserved. The causes of brain disorders in all three groups seemed to be different, and lysosomal disorders and congenital brain anomalies were frequently seen in cases in groups II and III, respectively. The dentato-rubro-olivary system is known to be involved in palatal myoclonus, and five out of 13 cases in group II showed myoclonic epilepsy. Compared with 95 cases without the CTT lesion, the changes in the pontine reticular formation were more closely associated with the CTT lesion than those in the inferior olivary nucleus. In conclusion, in cases of developmental brain disorders, the neuropathology of the symmetrical CTT lesion should be investigated.

Brainstem cavernous malformations: anatomical, clinical, and surgical considerations

Symptomatic brainstem cavernous malformations carry a high risk of permanent neurological deficit related to recurrent hemorrhage, which justifies aggressive management. Detailed knowledge of the microscopic and surface anatomy is important for understanding the clinical presentation, predicting possible surgical complications, and formulating an adequate surgical plan. In this article the authors review and illustrate the surgical and microscopic anatomy of the brainstem, provide anatomoclinical correlations, and illustrate a few clinical cases of cavernous malformations in the most common brainstem areas.

Relationship between multiple sclerosis intention tremor severity and lesion load in the brainstem

Intention tremor due to multiple sclerosis is clinically similar to cerebellar tremor. This study investigated, in 14 multiple sclerosis patients, the relationship between intention tremor severity and the lesion load in different infratentorial regions. Tremor amplitude was quantified during step-tracking tasks. The lesion load was measured on magnetic resonance images using an automated segmentation method. Intention tremor amplitude was significantly related to lesion load in the brainstem but not in the cerebellum. Specifically, tremor amplitude correlated with the lesion load in the contralateral pons, and patients with more severe tremor in both arms had a greater lesion load bilaterally in the pons. These results support the view that multiple sclerosis intention tremor is related to dysfunction of cerebellar inflow and/or outflow pathways.