The term subdural hygroma (SDHy) was first introduced in 1934 by Dandy [1] . It is a collection of cerebrospinal fluid (CSF), without blood, located under the dural membrane. It is commonly seen in elderly patients after minor trauma but can also be seen in children after infection [1] [2] .

In 1819, a subdural fluid collection after head injury was described by Pott. In 1916, Payr et al. presented four cases of subdural hygroma which were post traumatic and his original description was recorded under the name “meningitis serosa truamatica” [3] [4] .

Generally subdural space does not exist normally but a mild trauma can separate the space between dura mater and arachnoid mater creating a new space [5] which includes an interface layer composed of an arachnoid barrier layer and a dura border cell layer [6] .

There are different causes that may develop subdural hygroma. Traumatic brain injury still remains an important concern and one of the leading causes of subdural hygroma and comprises 5% - 20% of post-traumatic space-occupying lesions [2] [5] . Fate of traumatic subdural hygroma is classified into resolution, steadiness, development and evolution according to findings on computed tomographic scan [7] .

Other causes of subdural hygroma include, spontaneous subdural hygroma that may occur due to rupture of arachnoid cyst, and post-operative that develops after decompressive craniectomy, cranioplasty or shunt installation [4] [8] . Subdural hygroma may also develop in infants after infection where it may be misdiagnosed as subdural empyema [6] .

There is no specific symptomatology attributed to SDHy, the vast majority of patients are asymptomatic and the diagnosis is almost always discovered during brain neuroimaging. Some uncommonly reported symptoms include headaches, changes in mental status, nausea and vomiting, focal neurological deficits and seizures [5] . Sometimes, it may cause mass effect and become a life-threatening condition [8] . CT brain is the basic diagnostic neuroimaging study but advanced neuroimaging studies are occasionally needed [8] .

Management of SDHy is still a matter of controversy; many neurosurgeons suggest that the conservative treatment is the first option and that the surgical option is indicated when the mass effect and unfavorable clinical manifestations occur namely in the development or evolution types of SDHy [9] [10] . The objective of this prospective one-year clinical case study is to assess the different treatment modalities of SDHy (conservative and surgical) regarding the patients’ characteristics and clinical outcome, finding out the significant differences and the future recommendations.

This is a prospective one-year clinical case study involved 30 patients suffering subdural hygroma who were admitted to Assiut University Hospital during the period from November 2016 to November 2017.

Inclusion criteria:

All cases of subdural hygroma.

Exclusion criteria:

Patients with brain atrophy and cerebral palsy.

Patients who refused surgical open when indicated.

Patients with unavailable clinical or radiological data.

They were divided into two equal groups according to the type of management they have received (conservative or surgical). Patients’ characteristics including age, sex, mechanism of injury, clinical presentation and consciousness level (Glasgow coma scale {GCS}) at admission were studied and analyzed. Initial neuroimaging study of patients was performed through CT scan which was repeated during hospital stay. Information such as site of subdural hygroma, time of formation and presence of other concomitant brain damages were studied. The choice of treatment option depended on our judgment to clinical symptoms and signs. As a rule, the conservative treatment was our first treatment option and the surgical option was performed on the basis of GCS and the neuroimaging findings (Volume, location, mass effect, and degree of midline shift). In patients that were treated conservatively, there were no specific medications administered for subdural hygroma apart from close observation of the conscious level and blood electrolytes, and control of epilepsy. In patients who underwent surgery, 12 patients (80%) had burr hole drilling and drainage of the hygroma while 3 patients (20%) had subdural peritoneal shunt insertion and drainage. The clinical outcome was evaluated based on Glasgow Outcome Score system (GOS) at time of discharge and classified into five groups such as good recovery (stage 1), moderate disability (stage 2), severe disability (stage 3), persistent vegetative state (stage 4), and death (stage 5).

The data were then analyzed using Statistical Package for the Social Sciences (SPSS) software (version 20). Chi-square test was used for statistical analysis. Probability values of (P < 0.05) were considered statistically significant.

Male child, 7 years old presented with persistent headache and vomiting of 3 days duration, no history of trauma.

On examination:

Patient was fully conscious with no neurological deficits. MRI brain showed right cerebral crescent-shaped lesion (Figure 1).

Rt burr hole craniotomy with evacuation of the hygroma was done. The patient showed mederate clinical improvement, but suffered clinical deterioration two weeks later. CT brain was done to show recurrence or incomplete drainage of the hygroma (Figure 2).

The decision was to insert a right cysto-peritoneal shunt after which the patient showed marked improvement. Post shunt CT brain showed marked reduction in the size of the hygroma (Figure 3).

Subdural hygroma (SDHy) is mostly asymptomatic and has a regressive course, but sometimes, it may cause mass effect and become a life-threatening condition requiring surgical intervention [8] . In this study, alteration of the conscious level, neurological deficits and seizures were the main clinical presentation (70%, 36.5% and 13.5% respectively). Yousef-Zadeh et al. [11] reported alteration of conscious level and neurological deficit as the main presentation (62.5%) and headache in 50% of their patients. In the present study, 73.3% of our patients were below 40 years; this characterizes a younger and prevalent population. Zanini et al. [12] have reported close results with 50% of their patients aged between 16 and 40 years. Rambarki et al. [13] also have reported that most of their patients aged between 10 - 50 years of age as a late complication of head trauma.

For different authors, subdural hygroma is more prevalent in older patients with some degree of cerebral atrophy [14] [15] .

Regarding the gender, males to females percentage was 80% to 20% in our study Hamamoto et al. [16] also reported predominance of males by 82.3% in his study. Domination of males may be related to the fact that they are more liable to trauma than females because of the type of work and nature of lifestyle they both have.

In our study, head trauma was noticed to be the main etiology of SDHy formation in 46.7% of studied patients. Hamamoto et al. [16] also reported that 76.5% of his patients were post traumatic. The pathogenesis of this condition is not well understood. Some theories have claimed it to the formation of a one-way valve allowing the passage of CSF into the subdural space, caused by a traumatic tear of the arachnoidal mater or due to the rupture of an existing arachnoids cyst [17] . Other theories claimed it to the presence of underlying parenchymal or vascular pathology that causes a passive effusion into the subdural space [18] , while others claimed it to the new formation of subdural vascularized neomembranes with increased permeability of CSF in the arachnoids membrane due to the increasing transmembrane pressure gradient [19] .

As regard the location of SDHy on neuroimaging, SDHy was reported to be on the frontal and fronto-parietal region in 73.6% of our patients. Lee et al. [20] has reported similar results as 77% of hygromas were found in fronto-parietal region of his patients and he explained that by the effect of earth gravity on brain. As most patients lie on their back, the shrunken brain gravitates toward occipital area and therefore SDHy is formed in frontal area [20] .

In our study, SDHy was reported to be unilateral in 19 patients (63%) and bilateral in 11 patients (36%). Yousef-Chabok et al. [21] reported similar results in their study as they reported SDHy to be unilateral in 81.2% of patients and bilateral in 18.8% patients. But Lee et al. [20] reported that SDHy occurred bilaterally in 70% of his patients. Caldarelli et al. [10] also reported that the collections were bilateral in (53%) and were unilateral in (47%) of their patients.

Regarding the associated pathologies with SDHy, we reported that brain contusions were found in (50%) of our patients and subarachnoid hemorrhage was found in (33.4%) of them. In Liu et al. [7] study, most accompanying cranial pathologies were brain contusions followed by subarachnoid hemorrhage. Same results were reported by Yousef-Chabok et al. [21] as contusions were reported in 25% of their patients while subarachnoid hemorrhages were reported in 18.8% of their patients.

The association of subarachnoid hemorrhage and SDHy is explained as CSF flows caudally into the spinal subarachnoid spaces, rostral into the basal cisternal spaces and dorsally into the subarachnoid spaces over the cortical convexities and cerebellum. The subarachnoid hemorrhage alters the dynamics of CSF circulation and may cause brain damage leading to Blood Brain Barrier failure with accumulation of CSF in subdural space and formation of SDHy in patients with subarachnoid hemorrhage [21] .

Regarding the severity of brain insult which was assessed by Glasgow coma score (GCS), our patients were divided into 3 groups. Severe brain damage (GCS ≤ 8) that was encountered in 8 patients (26.7%), moderate brain damage (GCS 9 - 12) in 8 patients (26.7%) and mild brain damage (GCS 13 - 15) in 14 patients (46.6%). Yousef-Chabok et al. [21] reported that (18.7%) of their patients had severe brain damage, (50%) had moderate brain injury, and (31% 3) had mild brain damage.

According to the type of management our patients had received, they were divided into 2 equal groups with 15 patients in each group. One group had conservative management while the other one had surgical management. The clinical outcome was assessed by the Glasgow Outcome Score (GOS) as good or bad outcome. Regardless of the type of management, good outcome with mild or moderate disability was encountered in (63.3%) of our patients. While bad outcome was encountered in 11 patients (36.7%) (severe disability 3, vegetative 6, and 2 patients have died). Yousef-Chabok et al. [21] reported that (18.8%) of their patients had good outcome with no or mild disability, (75%) had good outcome with moderate disability, and (6.3%) had bad outcome with severe disability. Regarding the type of management in our study, the surgical group showed more favorable outcome than the conservative group as 11/15 patients (73.3%) had good outcome in the surgical group, while 8/15 patients (53.3%) had good outcome in the conservative group. Some authors reported that the conservative methods of management are the appropriate one as most of the hygromas resolve spontaneously [5] [22] . Others indicated that surgical methods of management are more appropriate especially in patients with mass effects and disturbed conscious level [23] .

Age plays an important role as a prognostic factor of SDHy. It is noticeable that younger patients showed good outcome than elderly ones. But yet it did not reach a statistical significance. It may be related to low presentation of elder patients (23%) in our study that already involves a small total number of patients. In our study, Group 1 (patients ≤ 40 years old) (23/30 patients), the outcome was good in 15/23 patients (65%) regardless of the type of management. They were 6/10 patients (60%) in the conservative group and 9/13 patients (69%) in the surgical group. Group 2 (patients > 40 years old) (7/30 patients), the outcome was good in 4/7 patients (57%) regardless of the type of management. They were 2/5 patients (40%) in the conservative group and 2/2 patients (100%) in the surgical group. Many authors reported similar results with a high percentage of good outcome in the younger groups of patients [11] [21] .

Severity of brain injury at time of admission is the main factor in determining clinical outcome of the patients regardless of the type of management, as shown in Table 4. It seems that clinical outcome depends mainly on the degree of GCS at time of admission regardless type of management. All 8 cases with severe GCS showed poor outcome in both groups of management. Whereas patients with mild and moderate GCS showed good recovery (19/22 patients, 86%) regardless of type of management they had (Table 4). Many authors reported similar results with a high percentage of good outcome in patients with mild and moderate Glasgow Coma Score [11] [21] [24] . Other factors as age, gender, site of SDHy or associated pathology had not yet reached a statistical significant value in determining the clinical outcome or even the type of management of patients with subdural hygroma.

Subdural hygroma is a benign lesion that may resolve spontaneously or with medical treatment. Its management is a matter of controversy. When the conscious level is a concern, surgical management should be considered. But the decision of surgical management may be affected by multiple factors especially GCS, neurological deterioration, and midline shift on neuroimaging. Generally, the surgical management option of SDHy is more favorable but the conservative management option should be the role as far as there is no concern on the patient’s conscious level.

Although we did not find a statistically significant difference between the surgical and the conservative management options for SDHy, there is a trend towards the surgical option when the conscious level is a concern.

The authors declare no conflicts of interest regarding the publication of this paper.

Almenzalawy, M.A., Essa, A.E.A. and Ragab, M.H. (2019) Subdural Hygroma: Different Treatment Modalities and Clinical Outcome. Open Journal of Modern Neurosurgery, 9, 208-220. https://doi.org/10.4236/ojmn.2019.93020