Management for traumatic chronic subdural hematoma patients with well-controlled shunt system for hydrocephalus.

Traumatic CSDH enlarged in two cases with VP or LP shunt system although the shunt valve pressure was increased to 200 mmH2O. In surgery, the hematoma cavity pressure was found to be 130 and 140 mmH2O, suggesting that to raise the shunt valve pressure is not effective for decreasing CSDH volume.

Introduction

It is not rare that nontraumatic chronic subdural hematoma (CSDH) can be induced by shunt surgery for hydrocephalus, because of over-drainage of cerebrospinal fluid (CSF) 1,2. In such cases, raising shunt valve pressure to maximum or transient ligation of the distal catheter of the diversion could successfully promote expansion of the compressed hemisphere. However, when traumatic CSDH occurs in a patient with a well-controlled shunt system for communicating hydrocephalus, it is questionable whether the same methods are effective. In this case report, the authors reviewed the effectiveness of raising shunt valve pressure based on the CSDH cavity pressure measured in surgery.

Case history

Case 1

An 83-year-old Asian male visited our clinic because of progressively worsening disorientation as he sustained mild head trauma 1 month ago, and head computed tomography (CT) showed bilateral thin CSDH (7 mm in thickness) (Fig.1 upper). The patient underwent ventriculo-peritoneal (VP) shunt for idiopathic normal pressure hydrocephalus (iNPH) 3 years ago. The shunt valve pressure had been controlled at 130 mmH2O using a Codman Hakim programmable valve system (Johnson & Johnson, New Brunswick, NJ, USA), and the shunt pressure was raised to 200 mmH2O. One month later, the patient visited our clinic because of a difficulty in walking due to mild left hemiparesis. Head CT showed enlarged right CSDH with mild midline shift to the left, although the left CSDH had disappeared spontaneously (Fig.1 middle). Burr-hole opening and irrigation of the hematoma was performed under local anesthesia. Before dural opening, the pressure in the CSDH was measured by sticking an 18-gauge needle into the hematoma through the dura mater with a manometer; the pressure was 140 mmH2O from the point at the external auditory meatus. The dura mater was then opened, and the dark red watery hematoma was irrigated. A drain tube was inserted into the hematoma cavity for drainage, and was removed the next day of surgery. Two weeks after surgery, the CSDH volume remarkably decreased on CT scan, and the patient was able to walk steadily by himself and discharged. After 1 month, due to recurrence of iNPH, his walking became unsteadily and orientation status deteriorated. The shunt valve pressure was changed to 130 mmH2O. In 1 month, the patient visited our clinic walking steadily with better orientation, and CT showed complete disappearance of the hematoma (Fig.1 lower).

Figure 1

Upper line: Very thin chronic subdural hematoma (CSDH) is bilaterally identified, but sulci are obvious in both hemispheres, and a midline shift is not recognized on computed tomography (CT). The thickness of the right CSDH is 7 mm, and the left is 5 mm. Middle line: One month after the shunt valve pressure was changed to 200 mmH2O, CT revealed a definite enlargement of the right CSDH. And the sulci are unclear in the right hemisphere due to hematoma compression, and a mild midline shift to the left is also recognized. CSDH of the left side is absorbed. Lower line: Bilateral CSDHs completely disappear on CT performed three months after surgery.

Case 2

A 78-year-old Asian man, who had hit his occipital 2 weeks ago, visited our clinic. Lumbar-peritoneal (LP) shunt was performed to the patient for iNPH 2 years ago. The patient was mildly disoriented but able to walk smoothly. Head CT showed bilateral thin subdural hygroma (Fig.2 upper), and shunt valve pressure was raised to 200 mmH2O from 120. One month later, the patient visited our clinic because of difficulty in walking and deterioration of cognitive function. Head CT demonstrated left CSDH with 12 mm in thickness compressing brain tissue (Fig.2 middle). Burr-hole surgery and measurement of the hematoma cavity were conducted in the same way in case 1, and the pressure was 130 mmH2O from the point of external auditory meatus. One week after surgery, the CSDH volume decreased on CT scan, and the patient was able to walk steadily and was discharged from our hospital. One month later, his walking became unsteadily and the shunt valve pressure was returned to 120 mmH2O. In 1 month, the patient visited our clinic walking smoothly, and left CSDH completely disappeared on CT scan (Fig.2 lower).

Figure 2

Upper line: Bilateral subdural space seems to be wide; however, sulci are well identified without brain compression. Middle line: One month after the shunt valve pressure was changed to 200 mmH2O, left CSDH is recognized on CT, and the hematoma compresses left brain hemisphere causing mild midline shift. Lower line: Three months after surgery, CT shows complete absorption of hematoma and expansion of bilateral hemispheres.

Discussion

CSDH patients demonstrate symptoms of increased intracranial pressure (ICP) such as headache, nausea, and papilledema 3. However, in our case, CSDH cavity pressure was 130 and 140 mmH2O, which was not higher than normal ICP. The authors attempted to decrease the volume of the CSDH by increasing shunt valve pressure to 200 mmH2O, expecting that enlargement of the lateral ventricles might contribute to expansion of the hemispheres and reduction of CSDH volume. However, CSDH became symptomatic, which rarely disappears spontaneously 4, and burr-hole surgery was finally necessary because of increased CSDH volume and compression of the right hemisphere. When CSF pressure exceeds CSDH pressure, shrinkage of the CSDH may be expected. CSF pressure in the lateral ventricles would rise to valve pressure level in noncommunicating hydrocephalus. In contrast, CSF pressure in the lateral ventricles is unlikely to reach 200 mmH2O in iNPH because CSF flows to cisterns from the ventricles freely in communicating hydrocephalus. The authors considered that CSDH cavity pressure of 140 mmH2O may be high enough to enlarge and compress the hemisphere focally despite of the level of shunt valve pressure in iNPH. We then concluded that either raising shunt valve pressure to maximum or ligation of the distal catheter of the shunt system is not effective for CSDH in patients with iNPH.