Transcranial sonography investigations of the cerebral blood flow disturbances after hypothalamic pituitary and brain stem surgery

Introduction

Cerebral blood flow (CBF) disturbances at focal lesions of the hypothalamopituitary system and brain stem structures are one of the unexplored and pressing questions of modern neurosurgery [1]. Transcranial duplex sonography (TCDS) is a widely used method for determination of the cerebral blood-flow velocity (FV) in neurosurgical patients.

Methods

We studied characteristics of cerebral hemodynamics by TCDS after hypothalamic and brain stem tumor excision in 186 patients. The data obtained were compared with CT-MRI data, clinical parameters and factors of neurohumoral regulation.

Results

Our study showed that FV disturbances were observed in 82% of patients after surgery for hypothalamic and brain stem lesion. The revealed FV disturbances were evaluated as vasomotor spasm of different degrees of manifestation; distress of FV was caused by a thrombosis of branches of cerebral vessels, hyperperfusion, hypoperfusion and infringements of venous outflow and CBF autoregulation. Stable neurological disorders were observed in 100% of patients at FV < 40 cm/s and >200 cm/s. At FV > 120 cm/s we observed 61% of patients with transient neurological disorders and 24% with stable, and at FV > 150 cm/s 22% with transient and 78% with stable neurological disorders. Middle cerebral artery (MCA)/internal carotid artery ratio >3.0 and FV > 120 cm/s and basilar artery (BA)/external vertebral artery ratio >2.0 with BA velocities >85 cm/s was associated with 92% sensitivity and 97% specificity for vasospasm in the MCA and BA accordingly. In 87% of patients with FV in MCA > 185 cm/s we observed focal ischemic brain lesions verified on CT scan. Fixed pathologic interactions between degrees of FV and factors of neurohumoral regulations suggest existing pathogenetic mechanisms of CBF disturbances in focal lesions of the hypothalamic pituitary system and brain stem. The dependence of FV disturbances and vasopressin plasma level was established. The revealed FV disorders allowed us to develop algorithms for therapy and preventing secondary ischemic brain lesions.

Conclusion

The investigation of FV by the TCDS method at focal brain lesions, together with MRI and neurological research, has allowed us to specify pathogenic mechanisms of CBF disturbances and algorithms for their therapy.