Predictive value of electroencephalography and computed tomography in childhood non-traumatic coma
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《美国医学杂志》
1 Departments of Pediatrics, Advanced Pediatrics Center, Post Graduate Institute of Medical Education and Research Center, Chandigarh, India
2 Departments of 'Radiodiagnosis, Advanced Pediatrics Center, Post Graduate Institute of Medical Education and Research Center, Chandigarh, India
Abstract
OBJECTIVES: To study value of electroencephalogram (EEG) and computed tomography (CT Scan) in predicting outcome of non-traumatic coma in children. METHODS: 100 consecutive children, between 2 months to 12 years, with non-traumatic coma, (Glasgow Coma Scale score < 8). Demographic and clinical data was recorded at admission. EEG and CT scan were done within 24 hours of admission. Etiologic diagnosis was assigned on basis of clinical data and relevant laboratory investigations. The outcome was recorded as survived and died. Among survivors it was graded as no disability, or mild, moderate, or severe disability. Odds ratio and/or relative risk (RR) with 95% confidence interval (C I) were calculated. RESULTS: EEG could be done in 60 patients (43 survived; 7 were normal, 8 had mild, 17 moderate and 11 severe disability) CT scan in 93 patients (60 survived; 11 were normal, 14 had mild, 21 moderate and 14 severe disability). A normal/borderline EEG was associated with good outcome (P = 0.001); 11 of 12 survived and of survivors 55% had no or mild disability. Electrocerebral silence on EEG was a predictor of death (OR = 44 -sub .95% Cl - 1.5-7372; P =0.01). An abnormal EEG was associated with significant increase in risk of disability among survivors (RR=2.6, 95% Cl= 1.2-5.4, P=0.03). Among CT abnormalities intracranial bleed suggested increased risk of death (RR = 2.1; 95% Cl - 0.8-5.3; P = 0.058), while, hydrocephalus was associated with better survival (RR = 0.7; 95% CI - 0.5 to 0.96; P = 0.029). However, hydrocephalus when compared with other abnormal CT scan findings, was associated with higher risk of moderate and severe disability among survivors (P= 0.046) CONCLUSION: A normal CT scan and EEG, and some of the specific findings could be helpful in predicting outcome in children with non-traumatic coma. EEG and CT scan should be done at admission in all patients with non-traumatic coma if feasible.
Keywords: Non-traumatic coma, Electroencephalography,; EEG; Computed lomography,- CT scan, Neuroimaging
Non-traumatic coma in childhood is an important pediatric emergency. Early prediction of neurologic outcome of comatose children remains a difficult challenge for the pediatric intensive care physician. Although certain clinical signs help in predicting the outcome, clinical examination per se has been found to be neither sensitive nor specific in determining prognosis. [1] Certain investigations like neurophysiologic tests and neuroimaging are therefore undertaken to assess the extent of brain injury. The prognostic value of these tests has been studied mostly in neonates, [2],[3] adults [4],[5],[6] and in traumatic brain injury. [7],[8] Very little information is available on the role of electroencephalogram (EEG) and Computed Tomography (CT scan) as predictors of nontraumatic coma in childhood. [9],[10] A prospective study was conducted to assess the value of EEG and CT scan in predicting outcome of non-traumatic coma in children.
This was part of a more comprehensive study to examine etiology, clinical signs and severity of non-traumatic coma in children and define predictors of outcome. The clinical data has been presented in a previous paper. [11]
Material and methods
This was a prospective observational study conducted at emergency unit of a Pediatric Hospital, which is a part of a large multispeciality tertiary care teaching and referral hospital. Institutional Ethics committee had approved the study. Informed written consent was obtained from the parents /guardian of the subjects.
Inclusion and exclusion criteria: All comatose children between 2 months to 12 years of age, presenting to pediatric emergency service of the Centre over a period of 10 months were eligible for inclusion in the study. Patients with history of trauma were excluded. Coma was defined as state of unresponsiveness without evidence of awareness of self or environment from which the patient cannot be aroused by vocal or sensory stimuli. A score of 8 or less on Glasgow Coma Scale (pediatric adaptation) was mandatory. [11]
Demographic and clinical data was recorded at the time of presentation to pediatric emergency. This included vital signs and coma severity score using Glasgow Coma scale modified for pediatric patients. Patients who survived were re-examined at the time of discharge to record the grade of disability. EEGs were recorded within 24 hours of presentation on an 18channel Nihon-Kohden Neurofax, 4188, EEG recorder. A pediatric neurologist (PS), who was blinded to the clinical data and outcome, reported the EEGs. The findings were graded according to the criteria laid by Tasker et al [9] with some modifications. CT scans were done at admission on Somotom, Siemens instrument and were assessed by a neuroradiologist (NKG).
Etiological diagnosis was assigned on basis of clinical and laboratory data. [11] The outcome was recorded as survived or died. Among survivors it was further graded as no disability, or mild, moderate, or severe disability. Detailed definitions used for various clinical diagnosis and gradation of disability at discharge have been presented earlier. [11]
Statistical Analysis: Descriptive statistics (frequency, percentages) were calculated. The association between study variables and the outcome was analyzed with help of chi-square test or Fisher's exact test (if the number in any cell was less than 5) and calculation of odds ratio (OR) and relative risk (RR) with 95% confidence interval (95% CI) using SPSS 10.0 and Epinfo 1.1 software.
Results
A total of 100 comatose children (65 boys, 35 girls) were included in the study. Thirty-five patients died and 65 survived. An EEG could be obtained within 24 hours of admission in 60 and a CT scan in 93 patients. Of the 60 patients on whom EEG was available 43 survived; 7 were normal, 8 had mild, 17 moderate and l l severe disability. Of 93 patients having a CT scan 60 survived; 11 were normal, 14 had mild, 21 moderate and 14 with severe disability.
The CT scan was normal in 24 patients. The commonest abnormality on CT scan was hydrocephalus, which was commonest in CNS infections group and included tubercular and bacterial meningitis and encephalitis table1. CT was helpful in etiological diagnosis in 6 patients with unsuspected intracranial bleed and in clearly defining the cause of coma in 57 patients.
EEG was normal or borderline in12 patients The commonest abnormalities seen on EEG were very low amplitude waves (33.3%) and diffuse high voltage slow activity (21.7%). Focal paroxysmal discharges were seen in 25%, mainly in those with CNS infections table1.
EEG and Outcome table2
Eleven of 12 patients with normal/borderline EEG survived whereas 4 of 5 children with electrocerebral silence on EEG died. Electrocerebral silence on EEG was associated with higher likelihood of death as compared to normal EEG (RR = 4.6, 95% CI = 0.8 - 26.7, P = 0.01) or all other EEG abnormalities (RR = 3.6, 95% CI = 0.6 - 21, P = 0.036). None of the other abnormalities on EEG showed a significant association with mortality.
Predictive Value of Electroencephalography and Computed Tomography
Among ll survivors having a normal EEG, 45% had no disability. In contrast only 2 of 32 survivors with abnormal EEG had no disability (OR 12,5; 95% CI = 1.5 - 126; P = 0.007), while 24 (75%) had either moderate or severe disability (OR = 5.5, 95% CI = 1.0 - 29.9, P = 0.03). Of the individual EEG abnormalities only diffuse high voltage slow activity showed significant association with occurrence of disability (RR = 1.8, 95% CI = 1.1 - 3, 1, P = 0.038) and moderate and severe disability (RR 2.4, 95% CI -1.1- 5.5, P = 0.028). Patients with focal discharge did not have significantly different outcome.
CT scan and outcome table3
Of all the abnormal neuroimaging findings, hydrocephalus was associated with better survival rate (78%) as compared to other abnormalities (RR of death= 0.69; 95% CI = 0.5 to 0.96; P = 0.029). In contrast, intracranial bleed was associated with a significantly higher mortality rate (67%) as compared to other abnormal findings on CT scans (RR = 2.1; 95% CI = 0.8-5.3; P = 0.058).
Among 16 survivors who had a normal CT, 10 (62.5%) were neurologically normal or had mild deficit, whereas out of 27 survivors with hydrocephalous, 18 (66.7%) had either moderate or severe disability (table3, P = 0.046). There was no significant difference in the frequency of moderate or severe disability in children showing hydrocephalus and those showing other abnormalities (P = 0.63).
Discussion
Assessment of prognosis of children in non-traumatic coma is difficult. The usefulness of EEG and CT scan in childhood non-traumatic coma is poorly documented although they are used routinely given their known contribution in similar contexts. This study fills in the gap of a prospective observational study assessing the role of EEG and CT scan in the prognostication of childhood non-traumatic coma.
In the present study, the first EEG was performed within the first 24 hours after admission as recommended by Synek. [12] There are very few previous prospective studies in pediatric coma that analyze the relationship between early electroencephalographic criteria and longterm outcome. [13],[14] Retrospective pediatric studies by Cheliout-Heraut et al [15] and Janati et al [16] evaluated victims of drowning with or without cardiopulmonary arrest. While continuous EEG monitoring or serial EEGs would possibly be more helpful, it is often not feasible to get serial EEGs in comatose children in most of the developing countries. Therefore, the authors studied the predictive value of a single EEG obtained at admission.
A strong association between electrocerebral silence on EEG and death, and between a normal EEG and survival, was observed. Tasker et al [10] also found that all of the comatose children with low amplitude EEG activity or electrocerebral silence had a poor neurological outcome. EEG patterns associated with poor outcome reported earlier by Johnston et al [17] included burst suppression, alpha like activity, very low amplitude activity and electro cerebral silence. A normal or borderline EEG with preservation of reactivity was associated with a significantly better neurological outcome as compared with abnormal EEG; more than 90% of survivors with abnormal EEG had neurological sequelae.
Among specific EEG findings high voltage slow activity was associated with significant increase in risk of disability. In some studies high-voltage EEG slow activity has been found to correlate with poor outcome [1] , however, Johnston et al [17] observed that generalized high-voltage slow wave activity had no predictive value. Similar to the study by Tasker et al [10] the authors did not find a significant difference in the outcome between patients with or without paroxysmal discharges on EEG. A discontinuous EEG and the presence of spikes or epileptiform discharges have been associated with an unfavorable outcome in children with hypoxic ischemic encephalopathy. [17] Malignant EEG changes were predictors of death in 42% of adults with hypoxic ischemic coma following sudden cardiac arrest; "uncertain" EEG findings had an uncertain prognosis. [18] However, EEG criteria must be interpreted cautiously because they may be altered by sedation. [19]
The contribution of neuroimaging in management of pediatric non-traumatic coma is well established. [2],[20] But, most of these are MRI based. Getting an MRI in a comatose child is often not feasible particularly in developing countries. CT scan is a useful tool in the assessment and management of raised intracranial pressure in non-traumatic coma. [21]In the present study CT scan provided useful diagnostic information on patients with unsuspected intracranial bleed (who had no history of trauma) and in defining the cause of coma and raised intracranial pressure in a very large number of patients. In addition to providing useful information on the extent of injury, valuable prognostic information could also be obtained from the CT scan. In the present study CT findings were useful predictor of outcome across various etiologic categories. Presence of intracerebral bleed was associated with a poor outcome as two-third of these children died, and 2 of the 3 who survived had moderate or severe disability. On the other hand presence of hydrocephalus on CT Scan, which happened to be the commonest CT finding; indicated a better chance of survival. Hydrocephalus, however, was associated with moderate and severe disability in twothird of the survivors. A normal CT scan was reassuring as more than 60% of patients with normal CT scan had no or mild disability.
In conclusion, predicting the outcome of children with non-traumatic coma continues to be a challenge for intensivists and pediatric neurologists. The present data suggest that both CT and EEG may have a supplemental role in early prognostication. A normal EEG at admission predicted significantly better chance of survival while an abnormal EEG, particularly with high voltage slow activity predicted very high risk of disability. CT scan besides being helpful in diagnosis was useful in predicting neurological outcome among survivors. Patients with hydrocephalous had a better chance of survival but had a significantly risk of moderate and severe disability. We conclude that wherever feasible, a CT scan and EEG should be obtained in children with non-traumatic coma with a Glasgow Coma Scale score <_8 to help in early prognostication.
References
1. Pampiglione G, Harden A. Resuscitation after circulatory arrest: Prognostic evaluation of early electroencephalographic findings. Lancet 1968; 1 : 1261-1265.
2. Biagioni E, Mercuri E, Rutherford M, Cowan F, Azzopardi D, Frisone MF et al. Combined use of electroencephalogram and magnetic resonance imaging in full-term neonates with acute encephalopathy. Pediatrics 2001; 107 : 461-468.
3. Karmel BZ, Gardner JM, Zappulla RA, Magnano CL, Brown EG. Brain-stern auditory evoked responses as indicators of early brain insult. Electroencephalogr Clin Neurophysiol 1988;71 : 429-442.
4. Rothstein TL. The role of evoked potentials in anoxic-ischemic coma and severe brain trauma. J Clin Neurophysiol 2000; 17: 486-497.
5. Chen R, Bolton CF, Young B. Prediction of outcome in patients with anoxic coma: a clinical and electrophysiologic study. Crit Care Med 1996; 24: 672-678.
6. Zandbergen EG, de Haan RJ, Stoutenbeek CP, Koelman JH, Hijdra A. Systematic review of early prediction of poor outcome in anoxic-ischaemic coma. Lancet 1998; 362: 1808 - 1812.
7. Carter BG, Taylor A, Butt W. Severe brain injury in children: Long-term outcome and its prediction using somatosensory evoked potentials (SEPs). Intensive Care Med 1999; 25: 722-728.
8. Ong L, Selladurai BM, Dhillon MK, Atan M, Lye MS. The prognostic value of the Glasgow Coma Scale, hypoxia and computerised tomography in outcome prediction of pediatric head injury. Pediatr Neurosurg 1996; 24 : 286-291.
9. Tasker RC, Matthew DJ, Helms P, Dinwiddie R, Boyd S. Monitoring in non-traumatic coma. Part I: invasive intracranial measurements. Arch Dis Child 1988; 63 : 888-894.
10. Tasker RC, Boyd S, Harden A, Matthew DJ. Monitoring in non-traumatic coma. Part II: electroencephalography. Arch Dis Child 1988; 63 : 896-899.
11. Bansal A, Singhi SC, Singhi P, Khandelwal N, Ramesh S. Nontraumatic coma. IndJPediatr 2006; 72 : 467-473.
12. Synek VM. Value of revised EEG coma scale for prognosis after cerebral anoxia and diffuse head injury. Clin Electroencephalogr 1990; 21 : 26-30.
13. Johnston B, Seshia SS. Prediction of outcome in non-traumatic coma in childhood. Acta Neurol Scand 1984; 69 : 417-27.
14. Mewasingh LD, Christophe C, Fonteyne C, Dachy B, Ziereisen F, Christiaens F et al. Predictive value of electrophysiology in children with hypoxic coma. Pediatr Neurol 2003; 28 : 178 - 83.
15. Cheliout-Heraut F, Sale-Franque F, Hubert P, Bataille J. Anoxie cer6brale par noyade chez 1'enfant: interet de 1'EEG dans le pronostic. Neurophysiol Clin 1991; 21 : 121-132.
16. Janati A, Erba G. Electroencephalographic correlates of neardrowning encephalopathy in children. Electroencephalogr Clin Neurophysiol 1982; 63: 182 - 91.
17. Mandel R, Martinot A, Delepoulle F, Lamblin MD, Laureau E, Vallee L, Leclerc F. Prediction of outcome after hypoxic-ischemic encephalopathy: A prospective clinical and electrophysiologic study. J Pediatr 2002; 141: 46-60.
18. Rothstein TL, Thomas EM, Sumi SM. Predicting outcome in hypoxic-ischemic coma: A prospective clinical and electrophysiologic study. Electroencephalogr Clin Neurophysiol 1991; 79: 101-107.
19. Madl C, Kramer L, Domanovits H, Woolard RH, Gervais H, Gendo A et al. Improved outcome prediction in unconscious cardiac arrest survivors with sensory evoked potentials compared with clinical assessment. Crit Care Med 2000; 28 : 721 -26,
20. Christophe C, Fonteyne C, ZiereisenF, Christiaens F, Deltenre P, De Maertelaer V et al. Value of MR imaging of the brain in children with hypoxic coma. Am JNeuroradiol 2002; 23 : 716 - 23.
21. Tasker RC, Matthew DJ, Kendall B. Computed tomography in the assessment of raised intracranial pressure in non-traumatic coma. Neuropaediatrics 1990; 21: 91 - 94.(Singhi Pratibha D, Bansal)
2 Departments of 'Radiodiagnosis, Advanced Pediatrics Center, Post Graduate Institute of Medical Education and Research Center, Chandigarh, India
Abstract
OBJECTIVES: To study value of electroencephalogram (EEG) and computed tomography (CT Scan) in predicting outcome of non-traumatic coma in children. METHODS: 100 consecutive children, between 2 months to 12 years, with non-traumatic coma, (Glasgow Coma Scale score < 8). Demographic and clinical data was recorded at admission. EEG and CT scan were done within 24 hours of admission. Etiologic diagnosis was assigned on basis of clinical data and relevant laboratory investigations. The outcome was recorded as survived and died. Among survivors it was graded as no disability, or mild, moderate, or severe disability. Odds ratio and/or relative risk (RR) with 95% confidence interval (C I) were calculated. RESULTS: EEG could be done in 60 patients (43 survived; 7 were normal, 8 had mild, 17 moderate and 11 severe disability) CT scan in 93 patients (60 survived; 11 were normal, 14 had mild, 21 moderate and 14 severe disability). A normal/borderline EEG was associated with good outcome (P = 0.001); 11 of 12 survived and of survivors 55% had no or mild disability. Electrocerebral silence on EEG was a predictor of death (OR = 44 -sub .95% Cl - 1.5-7372; P =0.01). An abnormal EEG was associated with significant increase in risk of disability among survivors (RR=2.6, 95% Cl= 1.2-5.4, P=0.03). Among CT abnormalities intracranial bleed suggested increased risk of death (RR = 2.1; 95% Cl - 0.8-5.3; P = 0.058), while, hydrocephalus was associated with better survival (RR = 0.7; 95% CI - 0.5 to 0.96; P = 0.029). However, hydrocephalus when compared with other abnormal CT scan findings, was associated with higher risk of moderate and severe disability among survivors (P= 0.046) CONCLUSION: A normal CT scan and EEG, and some of the specific findings could be helpful in predicting outcome in children with non-traumatic coma. EEG and CT scan should be done at admission in all patients with non-traumatic coma if feasible.
Keywords: Non-traumatic coma, Electroencephalography,; EEG; Computed lomography,- CT scan, Neuroimaging
Non-traumatic coma in childhood is an important pediatric emergency. Early prediction of neurologic outcome of comatose children remains a difficult challenge for the pediatric intensive care physician. Although certain clinical signs help in predicting the outcome, clinical examination per se has been found to be neither sensitive nor specific in determining prognosis. [1] Certain investigations like neurophysiologic tests and neuroimaging are therefore undertaken to assess the extent of brain injury. The prognostic value of these tests has been studied mostly in neonates, [2],[3] adults [4],[5],[6] and in traumatic brain injury. [7],[8] Very little information is available on the role of electroencephalogram (EEG) and Computed Tomography (CT scan) as predictors of nontraumatic coma in childhood. [9],[10] A prospective study was conducted to assess the value of EEG and CT scan in predicting outcome of non-traumatic coma in children.
This was part of a more comprehensive study to examine etiology, clinical signs and severity of non-traumatic coma in children and define predictors of outcome. The clinical data has been presented in a previous paper. [11]
Material and methods
This was a prospective observational study conducted at emergency unit of a Pediatric Hospital, which is a part of a large multispeciality tertiary care teaching and referral hospital. Institutional Ethics committee had approved the study. Informed written consent was obtained from the parents /guardian of the subjects.
Inclusion and exclusion criteria: All comatose children between 2 months to 12 years of age, presenting to pediatric emergency service of the Centre over a period of 10 months were eligible for inclusion in the study. Patients with history of trauma were excluded. Coma was defined as state of unresponsiveness without evidence of awareness of self or environment from which the patient cannot be aroused by vocal or sensory stimuli. A score of 8 or less on Glasgow Coma Scale (pediatric adaptation) was mandatory. [11]
Demographic and clinical data was recorded at the time of presentation to pediatric emergency. This included vital signs and coma severity score using Glasgow Coma scale modified for pediatric patients. Patients who survived were re-examined at the time of discharge to record the grade of disability. EEGs were recorded within 24 hours of presentation on an 18channel Nihon-Kohden Neurofax, 4188, EEG recorder. A pediatric neurologist (PS), who was blinded to the clinical data and outcome, reported the EEGs. The findings were graded according to the criteria laid by Tasker et al [9] with some modifications. CT scans were done at admission on Somotom, Siemens instrument and were assessed by a neuroradiologist (NKG).
Etiological diagnosis was assigned on basis of clinical and laboratory data. [11] The outcome was recorded as survived or died. Among survivors it was further graded as no disability, or mild, moderate, or severe disability. Detailed definitions used for various clinical diagnosis and gradation of disability at discharge have been presented earlier. [11]
Statistical Analysis: Descriptive statistics (frequency, percentages) were calculated. The association between study variables and the outcome was analyzed with help of chi-square test or Fisher's exact test (if the number in any cell was less than 5) and calculation of odds ratio (OR) and relative risk (RR) with 95% confidence interval (95% CI) using SPSS 10.0 and Epinfo 1.1 software.
Results
A total of 100 comatose children (65 boys, 35 girls) were included in the study. Thirty-five patients died and 65 survived. An EEG could be obtained within 24 hours of admission in 60 and a CT scan in 93 patients. Of the 60 patients on whom EEG was available 43 survived; 7 were normal, 8 had mild, 17 moderate and l l severe disability. Of 93 patients having a CT scan 60 survived; 11 were normal, 14 had mild, 21 moderate and 14 with severe disability.
The CT scan was normal in 24 patients. The commonest abnormality on CT scan was hydrocephalus, which was commonest in CNS infections group and included tubercular and bacterial meningitis and encephalitis table1. CT was helpful in etiological diagnosis in 6 patients with unsuspected intracranial bleed and in clearly defining the cause of coma in 57 patients.
EEG was normal or borderline in12 patients The commonest abnormalities seen on EEG were very low amplitude waves (33.3%) and diffuse high voltage slow activity (21.7%). Focal paroxysmal discharges were seen in 25%, mainly in those with CNS infections table1.
EEG and Outcome table2
Eleven of 12 patients with normal/borderline EEG survived whereas 4 of 5 children with electrocerebral silence on EEG died. Electrocerebral silence on EEG was associated with higher likelihood of death as compared to normal EEG (RR = 4.6, 95% CI = 0.8 - 26.7, P = 0.01) or all other EEG abnormalities (RR = 3.6, 95% CI = 0.6 - 21, P = 0.036). None of the other abnormalities on EEG showed a significant association with mortality.
Predictive Value of Electroencephalography and Computed Tomography
Among ll survivors having a normal EEG, 45% had no disability. In contrast only 2 of 32 survivors with abnormal EEG had no disability (OR 12,5; 95% CI = 1.5 - 126; P = 0.007), while 24 (75%) had either moderate or severe disability (OR = 5.5, 95% CI = 1.0 - 29.9, P = 0.03). Of the individual EEG abnormalities only diffuse high voltage slow activity showed significant association with occurrence of disability (RR = 1.8, 95% CI = 1.1 - 3, 1, P = 0.038) and moderate and severe disability (RR 2.4, 95% CI -1.1- 5.5, P = 0.028). Patients with focal discharge did not have significantly different outcome.
CT scan and outcome table3
Of all the abnormal neuroimaging findings, hydrocephalus was associated with better survival rate (78%) as compared to other abnormalities (RR of death= 0.69; 95% CI = 0.5 to 0.96; P = 0.029). In contrast, intracranial bleed was associated with a significantly higher mortality rate (67%) as compared to other abnormal findings on CT scans (RR = 2.1; 95% CI = 0.8-5.3; P = 0.058).
Among 16 survivors who had a normal CT, 10 (62.5%) were neurologically normal or had mild deficit, whereas out of 27 survivors with hydrocephalous, 18 (66.7%) had either moderate or severe disability (table3, P = 0.046). There was no significant difference in the frequency of moderate or severe disability in children showing hydrocephalus and those showing other abnormalities (P = 0.63).
Discussion
Assessment of prognosis of children in non-traumatic coma is difficult. The usefulness of EEG and CT scan in childhood non-traumatic coma is poorly documented although they are used routinely given their known contribution in similar contexts. This study fills in the gap of a prospective observational study assessing the role of EEG and CT scan in the prognostication of childhood non-traumatic coma.
In the present study, the first EEG was performed within the first 24 hours after admission as recommended by Synek. [12] There are very few previous prospective studies in pediatric coma that analyze the relationship between early electroencephalographic criteria and longterm outcome. [13],[14] Retrospective pediatric studies by Cheliout-Heraut et al [15] and Janati et al [16] evaluated victims of drowning with or without cardiopulmonary arrest. While continuous EEG monitoring or serial EEGs would possibly be more helpful, it is often not feasible to get serial EEGs in comatose children in most of the developing countries. Therefore, the authors studied the predictive value of a single EEG obtained at admission.
A strong association between electrocerebral silence on EEG and death, and between a normal EEG and survival, was observed. Tasker et al [10] also found that all of the comatose children with low amplitude EEG activity or electrocerebral silence had a poor neurological outcome. EEG patterns associated with poor outcome reported earlier by Johnston et al [17] included burst suppression, alpha like activity, very low amplitude activity and electro cerebral silence. A normal or borderline EEG with preservation of reactivity was associated with a significantly better neurological outcome as compared with abnormal EEG; more than 90% of survivors with abnormal EEG had neurological sequelae.
Among specific EEG findings high voltage slow activity was associated with significant increase in risk of disability. In some studies high-voltage EEG slow activity has been found to correlate with poor outcome [1] , however, Johnston et al [17] observed that generalized high-voltage slow wave activity had no predictive value. Similar to the study by Tasker et al [10] the authors did not find a significant difference in the outcome between patients with or without paroxysmal discharges on EEG. A discontinuous EEG and the presence of spikes or epileptiform discharges have been associated with an unfavorable outcome in children with hypoxic ischemic encephalopathy. [17] Malignant EEG changes were predictors of death in 42% of adults with hypoxic ischemic coma following sudden cardiac arrest; "uncertain" EEG findings had an uncertain prognosis. [18] However, EEG criteria must be interpreted cautiously because they may be altered by sedation. [19]
The contribution of neuroimaging in management of pediatric non-traumatic coma is well established. [2],[20] But, most of these are MRI based. Getting an MRI in a comatose child is often not feasible particularly in developing countries. CT scan is a useful tool in the assessment and management of raised intracranial pressure in non-traumatic coma. [21]In the present study CT scan provided useful diagnostic information on patients with unsuspected intracranial bleed (who had no history of trauma) and in defining the cause of coma and raised intracranial pressure in a very large number of patients. In addition to providing useful information on the extent of injury, valuable prognostic information could also be obtained from the CT scan. In the present study CT findings were useful predictor of outcome across various etiologic categories. Presence of intracerebral bleed was associated with a poor outcome as two-third of these children died, and 2 of the 3 who survived had moderate or severe disability. On the other hand presence of hydrocephalus on CT Scan, which happened to be the commonest CT finding; indicated a better chance of survival. Hydrocephalus, however, was associated with moderate and severe disability in twothird of the survivors. A normal CT scan was reassuring as more than 60% of patients with normal CT scan had no or mild disability.
In conclusion, predicting the outcome of children with non-traumatic coma continues to be a challenge for intensivists and pediatric neurologists. The present data suggest that both CT and EEG may have a supplemental role in early prognostication. A normal EEG at admission predicted significantly better chance of survival while an abnormal EEG, particularly with high voltage slow activity predicted very high risk of disability. CT scan besides being helpful in diagnosis was useful in predicting neurological outcome among survivors. Patients with hydrocephalous had a better chance of survival but had a significantly risk of moderate and severe disability. We conclude that wherever feasible, a CT scan and EEG should be obtained in children with non-traumatic coma with a Glasgow Coma Scale score <_8 to help in early prognostication.
References
1. Pampiglione G, Harden A. Resuscitation after circulatory arrest: Prognostic evaluation of early electroencephalographic findings. Lancet 1968; 1 : 1261-1265.
2. Biagioni E, Mercuri E, Rutherford M, Cowan F, Azzopardi D, Frisone MF et al. Combined use of electroencephalogram and magnetic resonance imaging in full-term neonates with acute encephalopathy. Pediatrics 2001; 107 : 461-468.
3. Karmel BZ, Gardner JM, Zappulla RA, Magnano CL, Brown EG. Brain-stern auditory evoked responses as indicators of early brain insult. Electroencephalogr Clin Neurophysiol 1988;71 : 429-442.
4. Rothstein TL. The role of evoked potentials in anoxic-ischemic coma and severe brain trauma. J Clin Neurophysiol 2000; 17: 486-497.
5. Chen R, Bolton CF, Young B. Prediction of outcome in patients with anoxic coma: a clinical and electrophysiologic study. Crit Care Med 1996; 24: 672-678.
6. Zandbergen EG, de Haan RJ, Stoutenbeek CP, Koelman JH, Hijdra A. Systematic review of early prediction of poor outcome in anoxic-ischaemic coma. Lancet 1998; 362: 1808 - 1812.
7. Carter BG, Taylor A, Butt W. Severe brain injury in children: Long-term outcome and its prediction using somatosensory evoked potentials (SEPs). Intensive Care Med 1999; 25: 722-728.
8. Ong L, Selladurai BM, Dhillon MK, Atan M, Lye MS. The prognostic value of the Glasgow Coma Scale, hypoxia and computerised tomography in outcome prediction of pediatric head injury. Pediatr Neurosurg 1996; 24 : 286-291.
9. Tasker RC, Matthew DJ, Helms P, Dinwiddie R, Boyd S. Monitoring in non-traumatic coma. Part I: invasive intracranial measurements. Arch Dis Child 1988; 63 : 888-894.
10. Tasker RC, Boyd S, Harden A, Matthew DJ. Monitoring in non-traumatic coma. Part II: electroencephalography. Arch Dis Child 1988; 63 : 896-899.
11. Bansal A, Singhi SC, Singhi P, Khandelwal N, Ramesh S. Nontraumatic coma. IndJPediatr 2006; 72 : 467-473.
12. Synek VM. Value of revised EEG coma scale for prognosis after cerebral anoxia and diffuse head injury. Clin Electroencephalogr 1990; 21 : 26-30.
13. Johnston B, Seshia SS. Prediction of outcome in non-traumatic coma in childhood. Acta Neurol Scand 1984; 69 : 417-27.
14. Mewasingh LD, Christophe C, Fonteyne C, Dachy B, Ziereisen F, Christiaens F et al. Predictive value of electrophysiology in children with hypoxic coma. Pediatr Neurol 2003; 28 : 178 - 83.
15. Cheliout-Heraut F, Sale-Franque F, Hubert P, Bataille J. Anoxie cer6brale par noyade chez 1'enfant: interet de 1'EEG dans le pronostic. Neurophysiol Clin 1991; 21 : 121-132.
16. Janati A, Erba G. Electroencephalographic correlates of neardrowning encephalopathy in children. Electroencephalogr Clin Neurophysiol 1982; 63: 182 - 91.
17. Mandel R, Martinot A, Delepoulle F, Lamblin MD, Laureau E, Vallee L, Leclerc F. Prediction of outcome after hypoxic-ischemic encephalopathy: A prospective clinical and electrophysiologic study. J Pediatr 2002; 141: 46-60.
18. Rothstein TL, Thomas EM, Sumi SM. Predicting outcome in hypoxic-ischemic coma: A prospective clinical and electrophysiologic study. Electroencephalogr Clin Neurophysiol 1991; 79: 101-107.
19. Madl C, Kramer L, Domanovits H, Woolard RH, Gervais H, Gendo A et al. Improved outcome prediction in unconscious cardiac arrest survivors with sensory evoked potentials compared with clinical assessment. Crit Care Med 2000; 28 : 721 -26,
20. Christophe C, Fonteyne C, ZiereisenF, Christiaens F, Deltenre P, De Maertelaer V et al. Value of MR imaging of the brain in children with hypoxic coma. Am JNeuroradiol 2002; 23 : 716 - 23.
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