Lunar” is a 3 year old DSH cat presented for neurological evaluation. Lunar’s appetite began to decline when the owner’s husband left the family several months prior to presentation. For 3 days prior to presentation she was completely anorexic. Two days prior to presentation she became ataxic and was salivating. She had 2 generalized seizures the day before admission. She had been vomiting bile in the week prior to presentation. On physical examination she was depressed and disoriented. PLRs were equal and reactive. Menace responses were present OU. The conscious proprioception and reflexes were normal. She had positional vertical nystagmus and marked cervical ventroflexion with any movement. Routine blood work had been done prior to examination and showed only a mild elevation of the alkaline phosphatase. A Toxoplasma gondii titer was negative. Lunar was anesthetized for placement of a PEG tube and CSF tap. Prior to placement of the PEG tube, the esophagus, stomach and upper small intestine were examined. The pylorus was difficult to enter and required considerable effort to penetrate. Multiple biopsies were taken and minimal histopathological abnormalities were found. A 20 French Pezzar catheter was placed with standard PEG technique. The spinal tap was performed a traumatically. The CSF contained 174 RBCs/ul and only 5 WBCs. Cytospin preparation showed RBCs and numerous PMNs. The neurological signs (cervical ventroflexion), history of prolonged anorexia, and findings of hemorrhage and mild inflammation in the spinal fluid lead to a clinical diagnosis of thiamine deficiency. Lunar was treated with injectable thiamine and tube feeding was started shortly after placement of the PEG tube. The ventroflexion was improved by the following morning but not completely resolved for another week. Lunar rapidly began to eat on her own and the PEG tube was removed in 2 weeks. At a one month recheck, Lunar had very mild cervical ventroflexion so daily oral supplementation with thiamine was started. The final diagnosis was thiamine deficiency secondary to prolonged anorexia. The anorexia was presumed to be caused by the family change, pyloric stenosis and secondary hepatic lipidosis. Thiamine deficiency causes grey matter hemorrhage in cats that particularly affects the brainstem. Lunar had brainstem as well as cerebral manifestations of the deficiency. I have found that a common cause of anorexia and vomiting in cats is pyloric stenosis. A 9 mm fiberscope will easily traverse the pylorus of an adult cat. The passage of the fiberscope through the pylorus with great care will dilate the pylorus and offers a long term resolution of this problem. If this is found to be secondary to inflammation or lymphoma, these problems must be treated also.