INTRODUCTION. The article discusses the problem of impaired cerebrospinal fluid circulation, in particular a rare form of hydrocephalus – low (“negative”) pressure hydrocephalus.

AIM. To improve the results of surgical treatment of patients with low-pressure hydrocephalus based on a comprehensive study of the pathomorphology and pathophysiology of the disease, improvement and optimization of surgical tactics. CLINICAL CASES. Two patients with acute and chronic GND. Patient N., 69 years old. Hospitalized in September 2022. A year before hospitalization, he underwent complex treatment for adenocarcinoma of the soft palate (removal and radiation therapy: 60 Gy for the soft palate and 50 Gy for the cervical lymph nodes). 6 months before hospitalization, he underwent surgery: removal of an arteriovenous malformation (AVM) of the right hemisphere of the cerebellum. Patient K., 73 years old, was hospitalized in November 2022 with a clinical picture of the Hakim – Adams triad (cognitive impairment, unsteady gait, urinary incontinence). According to CT scan of the brain, enlargement of the ventricular system with periventricular edema.

CLINICAL CASES. The condition of patient N. worsened within 1 week, according to the level of consciousness from 15 to 9 points on the Glasgow Coma Scale (GCS). According to CT scan of the brain: signs of internal hydrocephalus (ventriculomegaly, periventricular edema, smoothness of the sulci of the hemispheres, compression of the base cisterns). An emergency surgical intervention was performed: installation of an NVD with an ICP control sensor. 12 hours later, after a short-term improvement in the level of consciousness, the patient’s condition showed negative dynamics (level of consciousness 9 GCS points); on the control CT scan, signs of internal hydrocephalus remained. The NVD is functioning. When the ICP level was corrected to “negative” (–7 mm Hg), the patient regained clear consciousness. The ICP measured by the hydrostatic method was –100 mm H2O, which corresponded to the value obtained from the sensor. Patient K underwent a lumbar puncture and the pressure was measured using the hydrostatic method, which was 75 mm of water column in the supine position. In a sitting position, the pressure was 300 mm of water column from the level of the puncture needle, which corresponds to a pressure at the level of Monroe’s holes of –250 mm of water column, that is, subatmospheric. Moreover, according to a CT scan of the brain, the patient had an enlargement of the ventricular system with periventricular edema, and clinically symptoms of the Hakim-Adams triad. After performing a tap test (withdrawal of 30 ml) once, the patient’s cognitive abilities objectively improved, her gait became more coordinated when turning, and the number of steps required to move 5 meters decreased from 15 to 12, which was recorded on video. CSF removal was performed three times, once a day, 30 ml. After 3 days, the patient moved relatively normally and noted a significant improvement in urinary function (regression of urinary incontinence). Subsequently, the patient underwent ventriculoperitoneal shunting with an adjustable shunt with a minimum pressure set at 20 mm of water column.

In the presented clinical example, acute GND was probably provoked by previous radiation therapy, as well as surgery on the posterior cranial fossa. In the acute period of GND, it is necessary to install an NVD, with correction of ICP (up to subatmospheric pressure) in order to achieve the maximum level of consciousness of the patient. An available surgical method for permanent correction of ICP remains low-pressure ICP using methods of additional reduction of ICP (aspiration of cerebrospinal fluid from the shunt valve, “pumping”, verticalization of the patient) with a gradual decrease in their intensity over 3–4 weeks. It should be emphasized that the nosological form described above is only one of the clinical manifestations of the underlying disease. As for the mechanisms of the pathophysiology of chronic GND, they are currently unclear and require study. In this category of patients with the classic Hakim – Adams triad and hydrocephalic changes according to CT (MRI), when determining “normal” cerebrospinal fluid pressure in the supine position, a diagnosis of “normotensive hydrocephalus” is usually established. As for the mechanisms of the pathophysiology of chronic GND, they are currently unclear and require study. In this category of patients with the classic Hakim – Adams triad and hydrocephalic changes according to CT (MRI), when determining “normal” cerebrospinal fluid pressure in the supine position, a diagnosis of “normotensive hydrocephalus” is usually established. When measuring cerebrospinal fluid pressure in an upright position of the patient, it can be subatmospheric at the level of the foramina of Monroe.

CONCLUSION. Despite the fact that, in our opinion, the treatment tactics for such patients in any case involve the installation of a low-pressure ventriculoperitoneal shunt, studying the pathophysiology of impaired cerebrospinal fluid circulation in the above cases seems important for the development of non-invasive methods for correcting this condition.