Cerebral and brainstem lesions cause supranuclear gaze disorders which manifest as conjugate gaze deviations or conjugate gaze palsies. Focal seizures are usually due to structural lesions of the brain but are occasionally caused by systemic metabolic disturbances, of which nonketotic hyperglycaemia (NKHG) of diabetes mellitus is an example. Such life threatening medical emergencies may present as ocular movement disorders to an ophthalmologist. We present a case of NKHG induced focal seizure presenting as episodic conjugate eye deviation with face turn.
A 53 year old male patient attended our out patient department with complaints of episodes of deviation of both eyes to the right side along with face turn for the past three days. Each episode lasted for two minutes.The patient had two to three episodes per hour during these three days. During each episode the patient did not respond to verbal commands. He was a known hypertensive and diabetic for the past 15 years on regular treatment. His best corrected visual acuity in the right eye was 6/6 and in the left eye was 6/18. The right eye was pseudophakic and the left eye had immature cataract. Extraocular movements were normal in both eyes. Fundus examination showed moderate non proliferative diabetic retinopathy in both eyes. Colour vision was defective in the left eye and normal in the right eye. Central fields plotted by Bjerrum's screen showed an incomplete right homonymous hemianopia. A provisional diagnosis of supranuclear gaze disorder was made and the patient was referred for a neurologist's opinion who ruled out any other focal neurological deficit. CT scan showed an old infarction in the left middle cerebral artery region involving optic radiations. The blood sugar was 495 mg/dl and plasma osmolality level was 299 mosm/L. Electro encephologram (EEG) showed seizure activity.
Based on the patient's history, his raised blood sugar level and the EEG, his condition was diagnosed as non- ketotic hyperglycaemia (NKHG) induced focal seizure causing conjugate eye deviation to right side, with face turn and speech arrest. He was treated with insulin and intravenous fluids. After one week, the blood sugar was 110 mg/dl, plasma osmolality was 280 mosm/L and the epilepsy had ceased.
Acute cerebral lesions cause tonic ocular deviation, loosely classified as irritative or paralytic.1 Irritative deviations occur secondary to focal seizure activity or acute cerebral haemorrhage and the eyes are tonically deviated to the opposite side. Paralytic deviations are toward the side of the lesion and are associated with impaired gaze toward the opposite side, and are usually associated with a contralateral hemiparesis and hemianopia.
Focal seizures are usually due to structural lesions of the brain but occasionally are caused by systemic metabolic disturbances, of which NKHG of diabetes mellitus is a major example.2 Focal seizures may be the first serious manifestation of diabetes, preceded only by a short history of polyuria and polydipsia.3 The cause of the association between hyperglycaemia and focal seizures is still debated. In the presence of hyperglycaemia Gamma aminobutyric acid metabolism is increased and the levels of this important inhibitory neurotransmitter may be depressed resulting in a reduction of seizure threshold.4 Focal reduction in blood flow may be important and is known to occur in hyperglycaemia but even when this was severe enough to cause cerebral infarction focal seizure occurred only when blood glucose was high.4 Focal seizures associated with non ketotic hyperglycaemia are refractory to anticonvulsant treatment and respond best to insulin and rehydration.
Our patient had episodic conjugate eye deviation to the right side, face turn to the right side and speech arrest during the attack, with normal conjugate movements in between the attacks. Neurological examination revealed no focal deficit. Defective colour vision in the left eye was due to immature cataract. Based on the biochemical result of negative urine ketone bodies, raised plasma glucose and osmolarity level, his condition was diagnosed as focal seizure due to NKHG of diabetes mellitus. His CT scan showed an old infarction involving the left optic radiation causing incomplete right homonymous hemianopia . The usual cause for such focal seizure is focal injury to the cortex from anoxia, inflammation or metabolic disturbance.5 Thus a potentially life threatening situation with eye movement disorder may be presented to an ophthalmologist. The focal seizure ceased in our patient after correction of hyperglycaemia with insulin and rehydration.
Brick et al6 reported a similar case of a 66 year old diabetic male patient in whom seizures were triggered by deviation of the head and eyes to the right. After the onset of seizure he developed sustained clonic movements of the eyes to the right and speech disturbance. His blood sugar and serum osmolarity were raised. This patient had frequent seizures until the hyperglycaemia was controlled.
Non convulsive status epilepticus (NCSE) is an epileptic state in which there is some impairment of consciousness associated with ongoing seizure activity on EEG without obvious tonic clonic activity. Husain et al7 analysed risk factors and ocular movement abnormalities in 12 NCSE patients. Previous stroke, neurosurgical intervention, brain tumour and history of meningitis were the risk factors and nystagmoid eye jerks, hippus, repeated blinking, and persistent eye deviations were the eye movement abnormalities documented in his patients.
A thorough history and systematic evaluation of any eye movement disorder is essential for accurate anatomical localisation, aetiological diagnosis and management of ocular motility disorders.
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