Diagnosis of PCD should always be associated with a search for a primary origin of malignancy. This nervous system pathology is most commonly seen in ovarian, breast and small cell lung cancers or lymphoma (Peterson et al.
1992). In some patients, an ovarian tumor can be visualized by transvaginal ultrasound or by pelvic CT scan (Negishi et al.
2013). The neoplastic disease, however, is frequently at a very early stage and consequently a conventional diagnostic procedure may appear inconclusive. A number of studies show that the use of FDG-PET imaging is more sensitive and justified in this clinical context (Frings et al.
2005). An ovarian tumor that was not visible in transvaginal ultrasound appeared evident on the integrated PET–CT scan (Marchand et al.
2007). Surgery confirmed the diagnosis of a papillar serous adenocarcinoma of an ovary at stage IIB. An annual follow-up of another patient with PCD uncovered hyperactivity of an axillary region 5 years after the onset of neurologic symptoms (Mathew et al.
2006). The biopsy was consistent with metastasis of breast cancer. In some patients, combined FDG-PET imaging is the only one that can reveal the location of the malignancy (Rubello et al.
2005).
It is rather the antigenic specificity than particular neurologic syndromes that is more indicative for tumor location (Titulaer et al.
2011). The most specific for diagnosis, however, is the combination of both. In patients with anti-Yo, anti-Ri or anti-amphiphysin antibodies ovarian cancer should be suspected. If anti-NMDAR antibody is detected, it suggests coexistence of teratoma, including its immature type. The metanalysis of numerous studies conducted by Titulaer et al. (
2011) contains conclusions concerning management. In all these patients, transvaginal ultrasound is the investigation of choice. If it is negative, pelvic computed tomography or magnetic resonance imaging should be performed. In patients with antibodies that suggest ovarian cancer, an integrated FDG-PET/CT is indicated. It is important to perform it as soon as possible as combined PET/CT scan used in this context may significantly reduce the delay time to the surgery (Frings et al.
2005). If initial investigations do not detect any tumor, it is recommended to repeat them every 6 months for 4 years.
PNS develop as a result of the malignancy. Thus, it is not surprising that the neurological outcome in PCD may improve after tumor excision. Subsequent systemic immune therapy in the form of intravenous immunoglobulin, steroids and tacrolimus has also proven beneficial (Negishi et al.
2013). In young women affected with NMDR encephalitis associated with teratoma, surgical removal of the tumor in combination with plasma exchange, steroid and intravenous immunoglobulin may yield almost complete recovery (Tanyi et al.
2012). In some patients, a second-line immunotherapy (rituximab or cyclophosphamide) is necessary (Dalmau et al.
2011). It has been proven that early surgery combined with immunotherapy markedly improves outcome (Dalmau et al.
2008).
The question arises whether the diagnosis of paraneoplastic reaction commonly associated with ovarian tumor may itself constitute an indication for surgical management. Exhaustive laboratory and imaging investigations often remain inconclusive as to the presence and location of the tumor. Some reports suggest, however, that explorative surgery may reveal an occult neoplasm. In a group of 19 patients with both ovarian cancer and paraneoplastic cerebellar syndrome, laparotomy was performed (Hetzel et al.
1990). In seven women, there were no tumor symptoms and the laboratory as well as imaging investigation was normal prior to the surgery. The decision on operative management was taken exclusively based on the detection of onconeuronal antibodies. Surprisingly, all these patients had high-grade ovarian adenocarcinoma. Another remarkable observation made by the authors was either the lack of or limited volume of peritoneal invasion that are typical for advance ovarian cancer. In another study, laparotomy performed in some patients with PCD uncovered solely microscopic foci of ovarian cancer (Peterson et al.
1992). These findings are consistent with a report of
postmortem examination of a patient who died due to very severe paraneoplastic reaction affecting the nervous system (BRAIN et al.
1951). It revealed two very small ovarian tumors the size of which did not exceed 2 cm in diameter. These phenomena suggest that paraneoplastic reaction corresponds to an antitumor response. The history of a patient with PCD and abnormal CA-125 levels at postmenopausal age has also been reported (Mason et al.
1997). Though imaging studies did not suggest ovarian pathology, both laparoscopic salpingo-oophorectomy and endometrial biopsy were performed. The pathological examination did not confirm malignancy; however, the CA-125 level decreased to normal limits after ovarian resection. Another report presented the history of a patient with PCD whose retroperitoneal lymph node was enlarged to the size of 2.2 cm and Ca125 was highly elevated. Though during laparotomy adnexa were normal macroscopically, pathological examination revealed the presence of a microscopic adenocarcinoma of the fallopian tube (Frings et al.
2005). In a 53-year-old patient with anti-NMDAR encephalitis whose neurologic and psychiatric condition was deteriorating, the decision of abdominal laparoscopy was made in spite of normal abdominal and pelvic CT scan. Though both adnexa were macroscopically normal, the pathologic examination revealed a sex cord tumor (Tanyi et al.
2012). In a group of adult women affected with anti-NMDAR encephalitis, 56 % had ovarian teratoma (Florance et al.
2009). It should be noted that this fraction was significantly lower in adolescents and children (31 %). Ovarian resection in patients with PNS without clear diagnosis of cancer can be considered effective in terms of both malignancy and neurologic outcome. This can have considerable value in neoplasm therapy, for often the surgery reveals very early stage disease. It is also suggested by some authors that an early management of malignancy may prevent a more severe neurologic deterioration that may remain irreversible and highly debilitating otherwise (Vedeler et al.
2006; Tanyi et al.
2012). It has been confirmed that antitumor treatment improves overall survival in these patients (Shams’ili et al.
2003). In anti-NMDAR encephalitis, an emergent surgery contributes substantially to the final outcome and may enable even almost complete recovery (Dalmau et al.
2007; Florance et al.
2009; Tanyi et al.
2012). Even if serial CT or ultrasound is not suggestive of teratoma, an explorative surgery may prove informative. In a woman affected with anti-NMDAR encephalitis, blind oophorectomy was performed revealing an underlying teratoma and the resection was associated with significant neurological improvement (Johnson et al.
2010). In contrast, an excision of ovaries in combination with immunotherapy led to clinical improvement in another patient, but surprisingly the pathological examination was normal (Parratt et al.
2009). Taken together, it seems reasonable to perform an explorative laparoscopy or laparotomy in patients with paraneoplastic cerebellar syndrome or anti-NMDAR encephalitis whose imaging studies appear normal. After precise exclusion of other neurological aetiologies and considering the patient’s age, the salpingo-oophorectomy of macroscopically normal adnexa may appear beneficial.